Built in memory of the forty-nine men of Prince George’s County who died in World War I, the Peace Cross stands 40-feet-tall. (Amanda Voisard/For The Washington Post)

A federal appeals court on Wednesday declared unconstitutional a towering cross-shaped monument that has marked a major intersection in Prince George’s County for 90 years.

In a 2-1 ruling, the U.S. Court of Appeals for the 4th Circuit said the 40-foot-tall memorial maintained with thousands of dollars in public funds “has the primary effect of endorsing religion and excessively entangles the government in religion.”

The ruling by the three-judge panel does not mean the monument must be immediately removed from public land.

Supporters of the memorial, known as the Peace Cross, said the decision sets a “dangerous precedent” and vowed to appeal to the Supreme Court.

The question for the 4th Circuit was whether the cross — which stands at Maryland Route 450 and U.S. Route 1 in Bladensburg — is a memorial to local men lost in World War I or an unconstitutional government endorsement of religion that should be removed from public land.

Built in 1925 with funding from local families and The American Legion, the marble-and-cement cross honors 49 Prince George’s County men who died in the war. On the base are the words: valor, endurance, courage and devotion. A bronze tablet lists the names of the men and includes a quote from President Woodrow Wilson. The monument is part of a larger memorial park in the immediate area honoring veterans of several wars.

Even with the nonreligious elements, the court said Wednesday, “the sectarian elements easily overwhelm the secular ones,” making it an unconstitutional violation of the First Amendment that prevents the government from favoring a particular religion.

“The cross is by far the most prominent monument in the area, conspicuously displayed at a busy intersection,” wrote Judge Stephanie D. Thacker, who was joined by Judge James A. Wynn, Jr. in the opinion Wednesday by the appeals court located in Richmond.

Chief Judge Roger L. Gregory dissented, writing the First Amendment does not require the government to “‘purge from the public sphere any reference to religion.’”

The ruling comes as public displays of religion have been challenged in courts throughout the country. The Supreme Court has not given clear guidance, allowing some monuments with religious content to stand while rejecting others on public sites.

The Maryland-National Capital Park and Planning Commission, a state agency, owns the land and monument, and has spent about $117,000 to maintain and repair the cross, in addition to setting aside $100,000 for renovations.

Gregory wrote the majority “ignores certain elements of the memorial . . . and confuses maintenance of a highway median and monument in a state park with excessive religious entanglement.”

In his dissent, Gregory said it was significant that the monument had been public property for 50 years without a constitutional challenge.

Thacker disputed the importance of the lengthy period of time: “Perhaps the longer a violation persists, the greater the affront to those offended.”

In closing, Gregory quoted the words on the memorial honoring the veterans: “I cannot agree that a monument so conceived and dedicated and that bears such witness violates the letter or spirit of the very Constitution these heroes died to defend.”

Kelly Shackelford, president of First Liberty Institute, a nonprofit that helped The American Legion defend the cross, called the court’s decision an “outrageous ruling that sets a dangerous precedent and threatens the removal of memorials across the country.”

Shackelford said the religious-freedom organization would take the case to the Supreme Court. “We’re certainly not going to stop here,” he said. “If this is the law, everything else is in danger.”

In response to concerns about the impact on other memorials, the 4th Circuit opinion noted, for instance, the crosses at Arlington National Cemetery are smaller and displayed among religious symbols of many religions both on headstones and monuments. The ruling includes a photo of headstones from the cemetery.

The initial challenge in Maryland was brought by the American Humanist Association, a Washington-based group that represents atheists and others. The group did not dispute the monument is a memorial, but said in court that a giant cross on government property sends a message of exclusion in violation of the First Amendment.

A District Court judge in 2015 declined to order the cross removed from public land, saying it is a historically significant secular war memorial and that the government agency had a nonreligious reason for maintaining it.

In response to the 4th Circuit ruling on Wednesday, the humanist association’s executive director, Roy Speckhardt said, “government war memorials should respect all veterans, not just those from one religious group.”

If the Supreme Court does not agree to take up the Prince George’s case, the ruling would stand and a District Court judge would have to decide whether to order the removal of the cross.

At oral argument last December, Thacker and Wynn suggested the legal issues could be resolved outside of court by moving the site of the cross — or by cutting off the arms of the cross to form an obelisk.

Park and Planning Commission officials remain convinced the memorial is legal and have not “engaged in any serious consideration” of the idea of transferring the land to a private organization, according to Adrian R. Gardner, the agency’s general counsel.

The commissioners, Gardner said in an email Wednesday, will determine “how best to advance the community’s interest in light of the ruling.”