State officials agreed that the park favored the Confederate side and began to act on the request, first by holding a public hearing and then by choosing a precise location in the park.

“There were twice as many Union casualties there as Confederate,” said Charles Custer, 83, whose ancestors fought on both sides of the war and who supports the push for a Union monument. “They fought. They bled. And they are really not recognized anywhere.”

But the request has enraged many in the Sons of Confederate Veterans, which views the state’s decision as a betrayal of the small park’s legacy. As word spread, an online call to arms was issued by the national Confederate group’s leader to oppose the “Darth Vader-esque obscene obsidian obelisk” in what the group’s members see as the Second Battle of Olustee. Reinforcements were drafted, namely State Representative Dennis Baxley, the Republican chairman of the House Judiciary Committee and a member of the Sons of Confederate Veterans.

To descendants of the Confederates in North Florida, the move was perceived to be the latest salvo against this area’s values and traditions. The Civil War may have ended long ago, but in Florida, unlike much of the South, Yankees never stopped marching (or rolling) into the state, lured by milder weather and tax rates. Other newcomers arrived, too, slowly eroding the state’s Southern identity.

“The descendants of these families have moved over and moved over,” said Mr. Baxley of the Confederate side. A fifth-generation resident of North Florida, Mr. Baxley has drafted a bill to require legislative approval to alter commemorative sites. “You have 20 million people from all corners of the earth and the country. We have all these different perspectives here, and these descendants have accommodated that. But I think that diversity and respecting people’s ancestors applies to everybody.”