In the final moments leading up to the midnight deadline, Senate Republicans and Democrats were unable to agree on a stopgap funding measure to continue US Government services.
Throughout the day, government agencies are either letting their respective staff know they must stay home, or other federally funded organizations are talking about how they plan to handle the shutdown for the immediate future.
Thousands of federal employees will be placed on leave of absence meaning they won't report to work on Monday.
Whoever works for US agencies and departments that are considered nonessential, including agencies that pay out small business loans and process passport requests, will cease to work effective immediately until Congress is able to agree on a bill for the federal budget.
The White House has said that 1,056 members of the Executive Office of the President would be on leave of absence, and 659, considered essential, would continue to report to work.
Facts:
This is the first time a government shutdown has happened while one party, the Republicans, controls both Congress and the White House.
The vote was 50‑49, falling far short of the 60 needed to advance the bill. With a 54 seat majority in the Senate, the Republicans did not have enough seats to pass the bill without some support from the Democrats.
They want funding for border security including the border wall and immigration reforms, as well as increased military spending.
The Democrats have demanded protection from deportation of more than 700,000 undocumented immigrants who entered the US as children.
The Republicans added a sweetener in the form of a six‑year extension to a health insurance programme for children in lower‑income families. But Democrats want this programme extended permanently.
Trump accused the Democrats of being far more concerned with illegal immigrants than they are with their military or safety at the dangerous southern border.
But the leading Senate Democrat, Chuck Schumer, blamed the president, saying Trump was under pressure from hard‑right forces within the administration.
White House spokeswoman Sarah Sanders has warned that the president will not negotiate on immigration reform until Democrats stop playing games and reopen the government.
Stay tuned for the latest news on our radio stations
