Much of the national park system will close. Some popular parks like Yellowstone and the Grand Canyon will probably remain accessible, but visitor centers and campsites will be closed, and bathrooms aren’t likely to be maintained during the shutdown.

Some sites where access is easily controlled, including the Statue of Liberty, may be closed completely. The Smithsonian museums in Washington may have funds to stay open for a while, depending on how long a shutdown lasts. The National Zoo in Washington will close, but the animals will still be fed and cared for.

Closures could change over time if the shutdown persists, so if you’re planning a visit, check ahead.

The Federal Housing Administration and the Small Business Administration won’t be able to process new home or small business loans. The FHA shutdown will affect some people buying houses.

Depending on how long a shutdown goes, the State Department may stop issuing or renewing passports and visas.

The IRS will furlough most of its employees and stop issuing tax refunds. For now, that would only affect a small number of people, since few taxpayers file returns seeking refunds in December. But if a shutdown persists, the impact would grow.

What happens with government workers?

More than 800,000 federal workers will either be home without pay or working without pay for however long the government is closed, according to data compiled by Senate Democrats.

Those whose jobs are deemed “essential” — mostly public safety functions — will have to report to work without pay. That includes:

• More than 41,000 federal law enforcement and prison employees who work for the Justice Department will remain on duty.

• In the Transportation Department, thousands of air traffic controllers will keep planes moving during the busy holiday season.

• Homeland Security Department employees are hit the hardest, nearly 90% of them are considered essential, including more than 54,000 border control agents and 53,000 TSA agents.

Another 380,000 federal employees will be furloughed.