At one point, part of the second-floor ceiling collapsed while at least 20 firefighters were inside, Jenkerson said. “The entire ceiling came down around and on some of these guys,” he said.

No one was injured. Flames were largely extinguished by 9 p.m.

Kerry Manderbach, director of the museum, was on site Tuesday evening and said the manuscripts were largely housed on the first floor, and the fire, at least in the front of the building, was mostly on the second. Upstairs was a sanctuary or chapel, he said. Earlier in the day, a smoke alarm went off, and he ran into the museum and grabbed old manuscripts regarding Marxist revolutionary Che Guevara.

The museum opened in 2015, the 13th branch in a system created by David and Marsha Karpeles, who made their fortune in Southern California real estate. Collectors of historic documents for decades, they founded the first of their museums in 1983.

The building, a six-columned brick-and-stone church with arching stained-glass windows, sits just five houses off South Grand Boulevard, across the street from Compton Hill’s Reservoir Park, and on a block of mansions, luxury apartments and grand old St. Louis homes. Originally the Third Church of Christ, Scientist, the 107-year-old Greek Revival structure more recently housed the New Paradise Missionary Baptist Church.