Washington ? Cyclists, tourists and the occasional jogger stood out in the sea of Boy Scout troops wearing tan shirts, green shorts and thick green-and-red socks — some rolled hastily down to their ankles.

Spectators lined the sizzling sidewalks along Constitution Avenue in clusters wherever they could find shade.

The troops and accompanying bands were all smiles and appeared to be unaffected by the heat as they marched to celebrate the group’s 100th anniversary.

The Grand Centennial parade marked the first time since 1937 that Boy Scout troops had marched through Washington.

The last time, President Franklin D. Roosevelt invited them to convene on the National Mall for their first jamboree after a polio outbreak led to its cancellation in 1935.

On Sunday, troops young and old marched in the parade, and some stood cheering. Among them was Ted Parker, 71, of Oakton, Va. He joined Troop 1956 as a child in Portsmouth, N.H., and said he made lasting friendships while learning values that served him throughout his life.

Parker said most of the troops marching Sunday were probably too young to understand the importance of the program’s moral teachings, — such as being honest, respectful and open with others. Time, Parker said, would unveil the importance of these values to the young men.

“They grow up and they’re confronted with various issues throughout life, and I think they see the meaning,” he said. “As I come here and watch, it’s sort of generational in many ways.”

Bob Hoffman, 46 of Ijamsville, Md., stood on Constitution Avenue next to his 11-year-old son, Hunter — a third-generation Boy Scout — wearing a matching uniform. Bob looks forward to guiding Hunter toward appreciating the values his father passed on to him when he was Hunter’s age.

“It teaches young men and women how to think for themselves, how to work as teams,” Hoffman said. “It really gives them a good tool set for handling things in the future.”