BLADENSBURG, Md. — Five miles from the United States Supreme Court, a 40-foot-tall World War I memorial in the shape of a cross has stood for nearly a century. Now, it is at the center of a battle over the separation of church and state that may end up on the court’s docket.

The United States Court of Appeals for the Fourth Circuit declared this month that the Peace Cross, which sits on state-owned land in Maryland and has been maintained with public funds, was unconstitutional, a ruling that supporters of the monument warned could result in a “cleansing” of memorials on public grounds across the country.

An appeal would provide the justices an opportunity to weigh in on increasingly common disputes over religious symbols on government property. Scholars hope the case will further distill what is and is not an unconstitutional endorsement of religion.

The Peace Cross, which commemorates 49 fallen soldiers from Prince George’s County, looms over the knotted intersection of Maryland Route 450 and United States Alternate Route 1 in this old port town of 10,000 people. When the sun rises, the cross casts a shadow toward the bank of the Anacostia River, and when it sets, toward an industrial lot housing a King Pawn shop and a boarded-up Kelley’s Muffler.