Thousands of vehicles each day pass the Memorial Peace Cross, a landmark in Prince Georges County. (Mark Gail/FOR THE WASHINGTON POST)

The 40-foot-tall cross rises above the nearby shopping centers and neighborhoods, a well-known landmark that for more than 80 years has served as a gateway to Bladensburg and Hyattsville.

The Memorial Peace Cross honors 49 men from Prince George’s County who lost their lives during World War I.

Now the monument, which sits on state property, is the subject of a fight itself. The American Humanist Association, a Washington-based group that represents atheists and others, is calling for the cross’s removal, arguing that a religious image on public land violates the constitutional principle of the separation of church and state.

“There are no words on it that say ‘war memorial,’ ” said Fred Edwords, who brought the cross to the attention of the humanist organization. “It stands out there . . . like a very strong religious symbol.”

Bill Burgess, the association’s legal coordinator, said the cross is a Christian image, one that “does not represent the sacrifices made by non-Christian soldiers.”

But veterans and some community groups have vowed to fight to keep it as is, arguing that it was built on what was then private property at a time when military memorials were often overtly religious.

The controversy over the monument is the latest in a series of battles across the country over the meaning of the First Amendment’s guarantee that government will not endorse or impede the practice of religion.

When the Supreme Court decided a similar case in 2010, the justices narrowly rejected a complaint that a white cross in the Mojave Desert, honoring World War I soldiers, violated the First Amendment’s ban on endorsing one religion over any other. The majority said that the cross could be viewed as a more neutral symbol that honors heroes. A recent settlement allows a land swap that will put the property in private hands, where the First Amendment’s prohibitions would not apply.

Within the past year, the high court refused to review two other cases, letting stand lower-court rulings invalidating crosses anchored on public land in Utah and California. In the California case, involving a San Diego cross in a public park honoring veterans, a judge suggested that while the cross is illegal, there may be ways to modify the setting, similar to the Mojave Desert land swap.

Locally, the issue has come up in Loudoun County, where a creche outside the courthouse in 2011 was joined by nontraditional displays, including a skeleton Santa Claus mounted on a cross (which was twice ripped down) and atheist testimonials, such as “I can be moral without religion.”

Barry Lynn, a minister who heads Americans United for Separation of Church and State, said disputes over religious symbols in public spaces show no sign of abating.

“This happens a lot all over the country,” Lynn said. In the past few weeks, his organization helped negotiate removal of religious symbols with officials in Dugger, Ind., where a large cross with the words “Jesus Saves” was on publicly owned land, and in King, N.C., where a flag adorned with a cross was flying in a public park where veterans are honored.

Eleanor Roosevelt, an ardent civil libertarian, had said the battles over the wall between church and state may have to be refought in each succeeding generation, Lynn said.

“Sadly, this has been true,” he said.

Despite years of legal wrangling, there has been no clear-cut high-court ruling on the issue. The jurisprudence “is a mess,” said Maryland state Sen. Jamie Raskin (D-Montgomery), a constitutional law professor at American University. “Both conservative and liberal justices have said there is no way to know in advance what the rules are.”

And the Supreme Court rulings haven’t done much to refine the boundaries, with the justices preferring to view the issues on a case-by-case basis.

The Memorial Peace Cross in Bladensburg was dedicated in 1925 by the American Legion, and it has stood there ever since. But when Edwords, who lives in nearby Greenbelt, drove by it a few weeks ago, it made him uncomfortable. He called the American Humanist Association, where he formerly worked, and the group asked the Maryland-National Capital Park and Planning Commission, which owns and maintains the memorial, to remove it.

Edwords, the national director of the United Coalition of Reason, which helps promote atheist and agnostic groups, said the cross “leaves the wrong impression.”

“My government should be religiously neutral,” he said.

From a distance, the concrete and pink-tiled cross, made of colorized aggregate concrete by John J. Earley looks like a purely religious symbol, something that could easily be mistaken for an entryway to a church or cemetery, Edwords said. It is only on close inspection, when one is near enough to read the inscriptions, that it is clear that the cross is also a monument to the war dead. But getting close enough to understand its full meaning can be difficult. The cross sits on a grassy circle surrounded by state roads that are traveled by more than 50,000 cars a day, according to Maryland highway officials.

When it was first erected by local veterans, the cross stood on private property. But as traffic intensified, the state, which owns the nearby roads that encircle the monument, redesigned the intersection, and the cross was transferred to the park and planning commission in 1960.

Veterans groups said they will fight to preserve the monument.

“There are thousands of these around the country, mostly in the shape of a cross,” said Joe Davis, a Veterans of Foreign Wars spokesman.

He said the VFW would fight just as hard for a memorial in the shape of a Star of David or a Crescent, a symbol of middle eastern religions. “We obviously support preserving these national memorials,” he said.

Meanwhile the park and planning commission is researching the legal issues.

“We are doing our homework,” said general counsel Adrian Gardner. “We will certainly be prepared as soon as possible to protect the public interest, whatever that means.”