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American civil rights campaigner Martin Luther King arrives at London Airport in October 1961. Getty Images

Need a break from work, an excuse to volunteer or simply some extra weekend time? You're in luck: Monday is Martin Luther King, Jr. Day.

A federal holiday since 1986, MLK Day is a chance to honor King, a civil rights activist who President Ronald Reagan once called "a prophetic voice that reached out over the chasms of hostility, prejudice, ignorance and fear to touch the conscience of America." As such, many of the nation's offices and stores will suspend operations Monday in observance.

Here's what you need to know about what's open and closed:

Most government offices will be closed on Monday, among them local DMV offices and Social Security offices.

The U.S. Postal Service will not be delivering mail on Monday, but UPS and FedEx will be shipping like normal.

Most financial markets will be closed, including the New York Stock Exchange and Nasdaq. The Federal Reserve Bank, Bank of America, Citibank and TD Bank are also closed, though you may be able to access your account online in the interim.

Whether your school is closed depends on where you are — Georgia and Indiana are among the states in recent years that have chosen to hold classes on MLK Day to recover time lost during blizzards. But hospitals are generally always open.

In New York City, the subway is set to operate on a weekday schedule with only a few time changes, while the Long Island Rail Road will be on a modified holiday schedule. In Washington, D.C. the Metrorail will operate on a Saturday schedule every 12 minutes.

Stores, many of them with MLK Day sales, will be open on Monday. These include Walgreens, CVS, Walmart, Target, Publix, Best Buy and Trader Joe's. Restaurants open include Buffalo Wild Wings, Denny's, Taco Bell, McDonald's and Wendy's.