It’s official: This is now the longest government shutdown in US history.

We’ve reached day 22 of a political impasse between President Donald Trump and Congress that’s shuttered more than a quarter of the federal government. Nine federal agencies — from the State Department to the Transportation Department — have been adversely affected by the president’s refusal to sign any appropriations bills that don’t include more than $5 billion for a wall along the country’s southern border. Despite attempts to reach a deal, even threats from Trump to declare a state of emergency and divert funds to the border, it’s unclear how the showdown may end — or how much longer it will go on.

Caught in the crossfire are hundreds of thousands of federal employees, federal parks, and countless others dealing with delays for everything from tax refunds to farm aid.

Some 800,000 federal workers received an IOU in the mail on Friday instead of a paycheck. Both the House and Senate have voted to offer back pay to all federal workers affected by the shutdown. If signed into law, the bill would allow payments once a funding deal is reached, even for employees on furlough since the shutdown began. Until then, federal workers are being asked to wait it out.

The longer the shutdown stretches on, the more its negative effects are starting to creep into the lives of everyday Americans. Vacations are being ruined with widespread national park closures and airlines shutting down terminals over TSA callouts. And in some cases, the damage from the shutdown may be lasting. Just look to reports out of Joshua Tree National Park in Southern California, where inadequate staffing and security levels have led to vandalism and destruction of already endangered trees.

Government shutdowns are becoming more and more common

Shutdowns aren’t new: The US government has closed down 20 times over the past four decades. But if it seems like we’ve entered a renewed era of political brinksmanship, with a shutdown brewing seemingly almost every year now — with much higher stakes — you’re not wrong.

The concept of government shutdowns first came out of the Congressional Budget Act of 1974. As Vox’s Dylan Matthews explains, the first few shutdowns didn’t actually cause the federal government to grind to a halt. That changed in the early 1980s with a set of opinions issued by Attorney General Benjamin Civiletti declaring that in the event that Congress fails to pass new spending bills, federal agencies must be forced to close down at least in part, if not in full.

After a rash of short shutdowns in the ’80s, there were just three in the 1990s and none in the 21st century, until Republicans shut down the government for 17 days in 2013, attempting to delay Obamacare implementation.

One of those ’90s shutdowns previously held the record of longest government shutdown in US history: when President Bill Clinton and the GOP-controlled Congress feuded over balancing the federal budget.

Like many others, it occurred under a divided government (when the chambers of Congress and the presidency are controlled by opposing parties) and centered on a divisive wedge issue.

Under President Jimmy Carter, several funding battles centered on abortion funding under Medicaid. Congressional Democrats pushed back on funding Nicaragua’s anti-communist Contra guerrillas under Reagan.

As for Trump, he’s now in his third government shutdown in as many years, this time over a pet project and campaign promise to build a wall that isn’t necessary and few actually want.

The frequency, as well as the partisan intensity behind the shutdowns, lines up with the divide separating Americans along ideological extremes. Politicians have an appetite to leverage funding for key federal agencies over partisan issues, knowing that in the past, voters haven’t punished them in the ballot box for their maneuvers.

Add this to another new normal in Washington.