In January, Democrats will lose their unified control of Capitol Hill, ending a remarkable legislative streak that saw the party deliver on many of their campaign promises.

While Joe Biden and his party did not accomplish everything they set out to do, Democrats in Congress spent the last two years marshalling their thin majorities to pass consequential legislation that touches nearly every aspect of American life from water quality to marriage equality. Some of the most notable measures even earned Republican support.

As a new era of divided government dawns in Washington, with Republicans set to take control of the House on 3 January, here’s a look at what Democrats accomplished during the 117th Congress.

American Rescue Plan Act

Seven weeks into his presidency, Biden signed into law a $1.9tn economic stimulus plan designed to combat the coronavirus pandemic and begin repairing the nation’s frayed social safety net. The bill, passed by Democrats on a party-line vote, sent $1,400 stimulus checks to tens of millions of Americans and temporarily extended unemployment benefits.

It included billions in funding to speed up vaccination distribution and school reopenings and additional money to help state and local governments weather the pandemic-induced economic downturn. The legislation also temporarily increased the annual Child Tax Credit, a policy experts say helped halve child poverty in America before it ended.

In the months that followed, a debate flared over the legislation’s economic impact. Many economists credited the large-scale infusion of cash with spurring a rapid economic recovery while others argued that the plan, at least to some extent, contributed to inflation.

Establish Juneteenth as a federal holiday

In June 2021, Congress passed legislation to make Juneteenth, or 19 June, a federal holiday.

Juneteenth marks the events of 19 June 1865, when Union soldiers arrived in Galveston, Texas, to inform enslaved African Americans of their freedom, more than two months after the Confederacy surrendered. Calls grew to commemorate Juneteenth following nationwide social justice protests in the wake of the killing of George Floyd by police.

Create a House committee to investigate the Capitol attack

Formally titled the House select committee to investigate the January 6th attack, the nine-member panel was charged with investigating the events that led to the most grievous assault on the US Capitol in more than 200 years.

Democrats preferred a bipartisan independent commission to investigate the attack, similar to the one Congress established in the aftermath of 9/11. But Republicans stonewalled those efforts and in the end the House voted to create a select committee composed of seven Democrats and two Republicans, Liz Cheney of Wyoming and Adam Kinzinger of Illinois, both of whom have been ostracized by their party for criticizing Trump.

The committee held a summer of blockbuster public hearings that sought to chronicle what it charged to be a coordinated plot, instigated by Donald Trump, to subvert a free and fair election. With shocking testimony and slick video reels, the committee crafted a devastating portrait of a president willing to do anything to remain in power.

The panel issued the findings of its 18-month inquiry in a report released in late December, the result of more than 1,000 interviews and hundreds of thousands of documents. They referred Trump to the justice department for violating at least four criminal statutes, as well as his ally, lawyer John Eastman, on a conspiracy charge. Four lawmakers were referred to the House ethics committee, including Kevin McCarthy, who is expected to run for speaker of the House next year.

Bipartisan infrastructure law

Several presidents tried – and failed – to pass an infrastructure bill. But late last year, Biden signed into law the largest investment in US infrastructure in at least a generation.

Far narrower in scope than the $2.3tn plan Biden initially proposed, the sweeping public works package was nevertheless a hard-won, bipartisan victory, with 19 Republican senators voting in favor, including the minority leader, Mitch McConnell.

The infrastructure law provided for $550bn in new spending, investing in everything from the nation’s waterways and transit systems to its airports and electric grid. The bill also included funding for electric vehicle charging stations, as well as for zero- and low-emissions buses and ferries.

Confirm a supreme court justice

When supreme court justice Stephen Breyer announced his retirement, Biden had an opportunity to make good on his promise to nominate the first Black woman to the supreme court. His choice was Ketanji Brown Jackson.

In April, Jackson faced a grueling confirmation hearing before a deeply polarized Senate. She ultimately won approval in a 53-to-47 vote that was met with tears of joy and celebration by Black women and girls across the country. Jackson officially joined the court in late June, just after its controversial decision to overturn Roe v Wade, ending the constitutional right to an abortion.

Born in Washington DC and raised in Miami, Jackson is a graduate of Harvard Law School and previously served as a clerk for her predecessor, Justice Breyer. She is the first public defender to serve as a justice on the nation’s highest court.

Over the past two years, the Democratic-controlled Senate has confirmed a record-setting number of Biden’s judicial appointments, the overwhelming majority of whom are women and people of color. ​​

Gun-control legislation

After Congress’s failure to act in response to the killing of 26 children and educators at Sandy Hook elementary school in 2012, a bipartisan solution to the ever-rising toll of gun violence in America seemed unreachable.

But in June, following a spate of horrific mass shootings that included a racist attack on Black shoppers at a grocery store in Buffalo, New York, and the massacre of 19 students and two teachers at an elementary school in Uvalde, Texas, lawmakers finally came together to pass the first major gun-control legislation in a generation.

The bill toughens requirements for the youngest gun buyers, keeps firearms out of the hands of more domestic abusers and helps states implement “red flag” laws that make it easier for authorities to temporarily take away weapons from people deemed by a judge to be dangerous. It also includes funding for mental health and violence intervention programs as well as school safety initiatives.

Biden said the legislation was a “historic achievement”. Gun control activists also celebrated its passage, but said it was only a first step and much more aggressive action was needed.

The Chips and Science Act

The product of more than a year of negotiations between the House and the Senate, the so-called Chips and Science Act was designed to bolster US competitiveness with China by investing in the nation’s industrial and technological might.

The sprawling $280bn bill contains more than $52bn to expand the US’s domestic semiconductor manufacturing industry, after pandemic-induced supply chain pressures exposed just how dependent the country was on chips manufactured abroad.

The largest chunk of the money will go toward scientific research in areas like artificial intelligence, biotechnology and quantum computing. It would also create “regional innovation and technology hubs” with the aim of bringing jobs and economic growth to the most distressed parts of the country.

The package passed Congress with bipartisan support and was signed into law with great fanfare by the president, who has promoted the legislation at events around the country – and the world.

Aid for veterans exposed to toxic burn pits

With broad bipartisan support, Congress enacted legislation expanding access to healthcare and disability benefits for millions of veterans exposed to toxic burn pits during their military service.

The law, known as the Pact Act, helps veterans get screened and receive services for possible toxic exposures, such as Agent Orange during the Vietnam war, or toxins from pits used to burn military waste in Iraq and Afghanistan. It also expands the Department of Veterans Affairs’ list of conditions related to burn pit and toxic exposure, removing administrative obstacles for veterans to obtain disability payments.

The law was deeply personal for the president, who has suggested that exposure to burn pits in Iraq may have been responsible for the death from cancer of his elder son, Beau.

Inflation Reduction Act

Biden’s signature domestic achievement, the Inflation Reduction Act was a long-sought legislative pursuit that survived several overhauls and setbacks before finally becoming law in August 2022.

The version that became law was far narrower than the expansive vision Biden initially outlined, a plan known as Build Back Better. Even so, the climate, healthcare and tax plan was a legacy-defining accomplishment for the president, delivering on many of his party’s long-sought policy ambitions.

Taken together, the bill represents America’s largest ever investment in combating climate change. According to the White House, the climate initiatives contained in the plan put the US on track to cut greenhouse gas emissions by 40% below 2005 levels by the end of the decade. The legislation also includes investments in environmental justice, conservation and resiliency programs.

In an effort to reduce soaring healthcare costs, the Inflation Reduction Act allows the government to negotiate prescription drug prices for seniors on Medicare, extend federal health insurance subsidies and caps out-of-pocket costs for insulin at no more than $35 per month for Medicare beneficiaries.

The law also imposes new taxes on big corporations, setting a minimum corporate tax of 15% and boosts funding for the Internal Revenue Service in an effort to crack down on tax evasion. It is estimated that the law will reduce the federal budget deficit by about $300bn over 10 years.

At the signing ceremony, Biden hailed the measure as “one of the most significant laws in our history”. Now, as many of the law’s provisions begin to take effect, Democrats face the difficult task of explaining its many constituent parts to the public.

At midday on New Year’s Eve he tweeted: “Just 12 hours until many of the cost-saving provisions in the Inflation Reduction Act kick in for millions.”

Protections for same-sex marriage

When the supreme court overturned Roe v Wade, the conservative justice Clarence Thomas raised the prospect that marriage equality could be next. The threat set in motion an unexpectedly bipartisan scramble on Capitol Hill that resulted in landmark legislation protecting same-sex marriage.

The bill, known as the Respect for Marriage Act, provides a degree of relief to the hundreds of thousands of same-sex married couples in the United States by requiring federal and state governments to recognize lawfully performed unions regardless of sex, race or ethnicity.

But should the supreme court overturn Obergefell v Hodges, the 2015 decision that legalized same-sex marriage nationwide, the measure does not require states to perform same-sex marriages nor does it prevent them from banning the unions. It also includes a clause exempting religious organizations from any obligation to provide goods, services or accommodations for a celebration of a same-sex marriage.

Nevertheless, LGBTQ+ advocates and allies welcomed the legislation as a major step toward protecting a hard-won civil liberty. At a signing ceremony, Biden called the bill a step toward building a nation where “decency, dignity and love are recognized, honored and protected”.

Government funding bill

Days before Christmas, with the threat of a shutdown looming, Congress hastily approved a 4,155-page, $1.7tn spending bill to fund the federal government and its various agencies through the remainder of the 2023 fiscal year. The product of a chaotic round of 11th-hour negotiations, led by two retiring appropriators determined to cement their legacy with one final deal, the funding measure includes more than $858bn in defense spending.

Other big-ticket items in the measure included nearly $45bn in aid for Ukraine, a provision banning the use of TikTok on all government devices, a rewrite of the Electoral Count Act that was at the heart of Trump’s efforts to overturn the 2020 election, $40bn in disaster relief for communities struck by hurricanes, wildfires, floods and other environmental calamities this year.

After an agreement was reached, the bill was rushed through both chambers of Congress with unusual speed. It was approved with strong bipartisan support in the Senate but passed on a mostly party-line vote in the House, foreshadowing the brinksmanship to come when Republicans control the chamber next year.

Ukraine aid

Since the Russian invasion of Ukraine in February 2022, the US has committed more than $100bn in security assistance and humanitarian aid to the country. During a historic visit to Washington last month, the Ukrainian president, Volodymyr Zelenskiy, delivered an address to a join session of Congress in which he personally thanked Americans for their support.

In total, Congress has passed four tranches of emergency aid, including most recently, a $45bn package that was notably more than Biden requested. It passed as part of the year-end spending bill.

The funds have been used for a range of purposes, much of it military, economic or humanitarian in nature. That includes, for example, sending economic support for Ukrainian refugees as well as for security assistance to help train, equip and provide intelligence support to the Ukrainian military. A significant portion of the funds will be used to replenish stocks of US weapons sent to Ukraine.

Aid to Ukraine has so far been approved with overwhelming bipartisan support. But a contingent of far-right House Republicans have threatened to block future aid to Ukraine.

Reform the Electoral Count Act

In the wake of the assault on the US Capitol, a bipartisan coalition began working on an overhaul of the Electoral Count Act, the 1887 law that governs how Congress counts presidential electors.

Trump and his allies had sought to exploit ambiguities in the 135-year-old law to claim that the then vice-president, Mike Pence, in his role as president of the Senate, could delay the count or even toss out legitimate electoral votes from states that voted for Biden.

Pence dismissed the plan as unconstitutional. But the fringe theory flourished among Trump’s supporters, thousands of whom stormed the Capitol on 6 January in a failed attempt to stop Congress from certifying Biden’s victory.

Under a rewrite of the law, the vice-president’s role in counting electors is defined as purely ceremonial. It also raises the threshold for considering a challenge to a state’s electoral votes, making it harder for lawmakers to interfere in the process. The measure was passed as part of an omnibus spending package, the final major act of a Congress that was sworn in on the eve of the Capitol attack.

What Congress didn’t do:

The party in power did not accomplish everything it promised. Stymied by the Senate filibuster, Democrats could not rally enough support to weaken the rule and pass their legislative priorities on a party-line vote.

Democrats failed to codify Roe, after the supreme court ended the constitutional right to an abortion. Despite a streak of mass shootings, they could not find enough support in the Senate to ban assault weapons. A tide of restrictive voter laws went into effect without any response from Congress. Compromise eluded a bipartisan group working on police reform. Despite an 11th-hour push, there was no extension of the Child Tax Credit. And the 117th Congress adjourned without taking action to raise the debt limit, alarming analysts who have warned that Republican brinkmanship over the nation’s borrowing limit could lead to economic calamity.

With a divided government, the outlook for major legislative accomplishments is far less likely. Instead, Democrats are bracing for an onslaught of Republican-led investigations into the president, his family and his administration.