ROCKFORD, Ill. (WTVO) — Memorial Day serves as a day of remembrance for those who died while serving in the U.S. military, but why are sales on mattresses associated with the holiday?

The holiday stems from the American Civil War, which killed more than 600,000 service members — both Union and Confederate — between 1861 and 1865.

There’s little controversy over the first national observance of what was then called Decoration Day. It occurred May 30, 1868, after an organization of Union veterans called for decorating war graves with flowers, which were in bloom.

As early as 1869, The New York Times wrote that the holiday could become “sacrilegious” and no longer “sacred” if it focuses more on pomp, dinners and oratory.

In 1871, abolitionist Frederick Douglass feared Americans were forgetting the Civil War’s impetus — slavery — when he gave a Decoration Day speech at Arlington National Cemetery.

“We must never forget that the loyal soldiers who rest beneath this sod flung themselves between the nation and the nation’s destroyers,” Douglass said.

In the 1880s, then-President Grover Cleveland was said to have gone fishing — and “people were appalled,” said Matthew Dennis, an emeritus history professor at the University of Oregon.

By 1911, the Indianapolis 500 held its inaugural race on May 30, drawing 85,000 spectators. A report from The Associated Press made no mention of the holiday — or any controversy.

Once the holiday moved to the last Monday in May in 1971, “the traditional barriers against doing business began to crumble,” authors Richard Harmond and Thomas Curran wrote.

As TV and newspaper ads began to circulate, businesses began to notice a link between national holidays and increased sales, since retail stores are open and many workers have the day off.

Sleep Advisor says that May is the best month of the year to purchase a mattress as brands typically release new products in June.

Memorial Day Weekend has also become synonymous with the official start of Summer, which is when many people move and may be in need of new furniture.

It’s also one of the best times of the year to get a deal on a new car.

Meanwhile, Jason Redman, 48, a retired Navy SEAL who fought in Iraq and Afghanistan, said he’ll be thinking of friends he’s lost. Thirty names are tattooed on his arm “for every guy that I personally knew that died.”

He wants Americans to remember the fallen — but also to enjoy themselves, knowing lives were sacrificed to forge the holiday.

The Associated Press contributed to this report.