In what had long been celebrated every May 30 to honor America's fallen soldiers, Memorial Day officially became a federal holiday in 1971, observed on the last Monday in May.

Businesses increasingly have chosen to stay open on the holiday, leading to what is now one of the biggest retail sales and travel weekends of the year.

Here's what is open and closed this year on Memorial Day:

Government offices, post offices, courts and schools are closed.

U.S. stock markets and banks are closed Monday.

Most FedEx and UPS pickup and delivery services will also not be available on Memorial Day.

Warehouse membership club Costco said it would close on Memorial Day, but the vast majority of retailers will be open, with many trying to lure customers with big promotional sales. Hours may vary by location.

Memorial Day is also considered the unofficial opening of the summer travel season. Auto club AAA projects 43.8 million travelers will head 50 miles or more from home over the holiday travel period, an increase of 4% from last year. If those projections are accurate, that would come close to 2005's record of 44 million Memorial Day weekend travelers.

AAA projects 38.4 million people will travel by car over the weekend -- the highest number for that holiday since AAA began tracking it in 2000 -- and that another 3.5 million people will travel by air.