(NEXSTAR) — Though Memorial Day may seem randomly placed on the calendar, there’s a reason it always falls on the last Monday of May.

To understand, you need to go back roughly 155 years.

It was 1868, three years after the Civil War had ended. Major General John A. Logan, the leader of the Grand Army of the Republic (an organization of Union veterans), declared that May 30 should serve as Decoration Day. On that day, Logan wanted Americans to place flowers on the graves of the war dead, according to the U.S. Department of Veterans Affairs. Falling far enough into the spring, the hope was that flowers would be in bloom nationwide.

Records show the first large observance of Decoration Day was held at Arlington National Cemetery that year. Flowers were spread on the graves of Union and Confederate soldiers alike, and Logan’s order for his post called for graves to be decorated “with the choicest flowers of

There are multiple cities that claim to have paid tribute to those killed in the Civil War before Logan’s declaration, many of which were located throughout the South, the VA explains. Among those was Carbondale, Illinois, where, according to a stone in a cemetery, the first Decoration Day ceremony was held in late April 1866.

As the story goes, Civil War veterans were waiting for a church service to begin when they noticed a woman with two young children place flowers on a small, unmarked grave. The veterans then collected nearby wildflowers and decorated soldiers’ graves in the cemetery.

The group then decided flowers should be placed on the graves of the war dead in Woodlawn Cemetery across town. On April 19, 1866, the veterans, along with others in the community, walked from an area church to Woodlawn Cemetery to place flowers on the aforementioned graves.

Before their procession, though, Logan — who lived in Carbondale during wartime — spoke to the group. Two years later, Logan signed an order to designate the day of observance.

Despite the obvious connection between Carbondale and then-Decoration Day, Congress and President Lyndon Johnson declared another town — Waterloo, New York — as the official birthplace of the day in 1966. According to records, in May 1866, the city, located about 50 miles west of Syracuse, is said to have honored Civil War veterans by closing businesses, flying flags at half-staff, and parades.

Though it isn’t clear when exactly people stopped calling the day Decoration Day, by the late 1800s, many were referring to it as “Memorial Day,” according to the American Battle Monuments Commission.

Regardless of its origin, Memorial Day became a national holiday in 1971. It was permanently placed on the last Monday of May and designated as a day to honor those who died in all American wars.

Memorial Day isn’t to be confused with Veterans Day, which honors those who fought in American wars and were discharged under conditions other than dishonorable. Another military holiday in May, Armed Forces Day, honors those currently serving in the U.S. military.