Garbage will pile up in the streets of the capital, the Statue of Liberty will close and astronauts will stay home if the Congress fails to reach a budget deal and the government shuts down.
Government services that are deemed as nonessential run out of funding at midnight on Friday without an agreement between Republicans and Democrats on spending for the rest of the fiscal year.
If lawmakers cannot break the logjam, some 800,000 employees will be sent home without pay when federal agencies close indefinitely.
The famed Yosemite National Park in California will close to new visitors from Saturday, but will give tourists already in its hotels and campgrounds until Monday to pack up and leave.
There are thousands of people depending on this, said Commerce Department employee Trish Lister who did not know if she would be furloughed. I'm not worried for myself but I am disgusted by the children in Congress, particularly the Tea Party, she said.
With a midnight deadline looming, the White House and Congress scrambled to break the budget impasse.
Republicans, encouraged by the fiscally conservative Tea Party movement, pushed for deep cuts in the spending bill. They say the government needs to slim down to close the fiscal deficit of $1.4 trillion. But Obama's Democrats say cuts that are too steep would hinder economic recovery.
A shutdown would be felt thousands of miles away by U.S. troops in Afghanistan and Iraq and there could be a high political cost for the lawmakers who let it happen.
Military personnel will keep working but not receive their paychecks until the shutdown ends.
They will get paid but it's a disruptive thing when you've got young military families trying to make ends meet, sometimes living from paycheck to paycheck, Republican Senator Jon Kyl said.
Some astronauts, but not those in training for space station missions or active-duty military officers, would be affected by the shutdown.
The astronaut corps, at large, will be furloughed, said Nicole Cloutier-Lemasters, spokeswoman at the Johnson Space Center in Houston, Texas. Those remaining active and on duty would be about one third of the 61-member astronaut corps.
Downtown Washington will be a lot quieter next week if there's a shutdown. Government agencies and prime tourist sites like the Smithsonian Institution museums will close.
Unlike other U.S. cities, the capital is prohibited from spending local dollars in the event of a federal budget impasse. It will not collect garbage for the first week of a shutdown, and parking meters will not be routinely monitored, although police can still give tickets for illegal parking.
A group of Washington residents threatened to dump their garbage at House of Representatives Speaker John Boehner's basement apartment in the city in the event of a shutdown.
They warned of a protest on Saturday morning against the Republican lawmaker in a Facebook site named, If Boehner shuts down the government I am taking my trash to his house.
Federal workers would be the worst affected. Unlike soldiers, they might never be reimbursed for the workdays they lose, although some agencies are expected to eventually pay federal employees who have to stay away from work.
Forecasting firm Macroeconomic Advisers said a week-long shutdown would cut roughly 0.2 of a percentage point from second quarter U.S. economic growth.
A Wall Street Journal/NBC poll found that voters would be split over whom to blame if the government does shut down. Thirty-seven percent would blame Republicans in Congress, 20 percent would blame Democrats and 20 percent would blame Obama. Seventeen percent would hold all of them responsible.
Unlike the last two shutdowns, both of which occurred in the 1990s, this one would take place during tax preparation and filing season. That would delay tax refunds to Americans who filed a paper -- rather than electronic -- tax return, which covers about 30 percent of the total number of returns.
(Additional reporting by Irene Klotz in Florida and Daniel Levine in San Francisco; Editing by Vicki Allen)