The Washington County Sheriff's Department, which might provide at least part of the event security, learned Monday, Capt. Doug Mullendore said. The town has not yet planned a meeting with police.
Lt. Greg Johnston of the Maryland State Police in Hagerstown couldn't be reached for comment Wednesday.
Gordon Young, the World Knights' imperial wizard, said he's starting to publicize the event among white supremacy groups.
He said he probably will talk about various topics at the rally, including hate letters that circulated in Hagerstown.
Although the World Knights chapter told the town in writing that it wants to use the park, it apparently does not need a permit.
"The park's a public facility," Boonsboro Mayor Charles F. "Skip" Kauffman Jr. said. He would not comment on the rally and referred all questions to the police.
Kauffman said there is no charge to use the park or its pavilion, which is what the World Knights requested.
The same Klan chapter held a march in Sharpsburg on Aug. 28, 2004.
Young, who lives in Hagerstown, predicted at the time that about 100 supporters would attend.
Instead, about 10 people marched on two blocks of Hall Street in front of a crowd that was cordoned off. About 100 police officers also watched, tightly controlling the event and the crowd.
After the march, police let only parade participants into Lonnie L. Crampton Memorial Park, and not the public, so a rally was scrapped.
The same day, a group of southern Washington County residents held separate events in Sharpsburg and Keedysville to promote tolerance, drawing many more people than the march.
The Rev. Malcolm Stranathan of Salem United Methodist Church in Keedysville, who helped form the tolerance group, said Wednesday he'd like to see a similar effort this year.
He hadn't heard about the new Klan rally until The Herald-Mail contacted him.
"It's kind of disappointing that they feel they need to do this," Stranathan said.