A site marker on the sidewalk off Main Street in Fairfax City, Va., marks the birthplace of the Confederate battle flag. (Evelyn Hockstein/For The Washington Post)

The Confederate battle flag, a controversial symbol that was condemned this week by much of the political spectrum, was born a few miles outside Washington during the first major land battle of the Civil War.

A simple roadside marker in Fairfax City describes how “amid the smoke of combat” during the First Battle of Manassas in 1861, Confederate soldiers had trouble distinguishing which troops were carrying the American flag and which were hoisting what was then the flag of the rebellious Southern states.

That’s because the first Confederate flag resembled Betsy Ross’s Colonial-era flag, with red and white stripes aligned next to a ring of white stars on a blue field.

Near what is now Main and Oak streets in Fairfax City, Confederate Gens. Pierre Gustave Toutant-Beauregard and William L. Cabell approved the design for a new flag: square and red, with diagonally crossed blue bars and stars — the Confederate battle flag.

“There was a lot of confusion” during the early part of the Civil War, said Michael Shumaker, a retired U.S. Navy officer who championed the effort to install the historic marker in 2007. “There was a need to have a flag that was distinctly different.”

The outnumbered Southerners won the First Battle of Manassas, also known as the First Battle of Bull Run, sending a strong signal to stunned Northerners that the civil war would be long and hard.

On Wednesday, as cars and a few pedestrians passed by the marker, several people interviewed by a Washington Post reporter said they never realized that the sign was there.

But once they examined it, they — like much of the nation — had ready opinions about what the flag means in the aftermath of last week’s fatal shootings of nine African Americans inside a historic black church in Charleston, S.C. Authorities say the alleged shooter, Dylann Roof, used the Confederate flag in a racist manifesto posted online before the shooting.

“I don’t like it,” Delia Espinoza, 40, a Mexican immigrant who lives in an apartment complex near the site of the historic meeting. “But, at the same time, this is a free country,” she said in her native Spanish.

Shah Khokker, 21, said he likes the marker’s historic significance but thinks the Confederate flag should no longer be publicly flown. “Who won the war? The U.S. won the war,” Khokker said.

South Carolina Gov. Nikki Haley (R) has moved to end the practice of flying the flag on the statehouse grounds, and Virginia Gov. Terry McAuliffe (D) and Maryland Gov. Larry Hogan (R) have called for removing the symbol from state license plates.

But the issue is complicated, and opinions vary. Jim Webb (D), a former U.S. senator and a potential 2016 presidential candidate, defended the flag’s historic significance Wednesday.

And on Main Street in Fairfax City, Mike Mpalong, who is African American, applauded the marker and defended the use of the flag.

“I really don’t think they should take it down,” the 20-year-old said, explaining that he was worried about a racial backlash, among other things. “Taking down the flag would just create more stuff, more problems.”

Besides, Mpalong added, “It’s a part of history.”