JEFFERSON CITY, Mo. (AP) — Tours of the old Missouri State Penitentiary in Jefferson City turned a profit last year for the first time, and tourism officials think that's only going to improve.

More than 19,000 people from 23 countries visited the former prison in 2012, generating about $275,000 in revenue — roughly $35,000 of which was profit, the Jefferson City News Tribune reported ( ).

"We expect continual growth," said Shelley Klebba, the interim executive director for the Jefferson City Convention and Visitors Bureau.

Ticket sales account for most of the revenue, while expenses include the guides' salaries, advertising and supplies such as lights, signs and trash bags.

Officials said the expenses declined in 2012 partly because the Jefferson City Convention and Visitors Bureau spent $40,000 last year to buy 5,000 copies of a book about the former prison written by a local historian who worked there. In addition, officials last year reduced spending on print advertising to focus more online.

Eventually, tour officials said they would like to hold hourly tours for anyone who arrives. Currently, the tours of the prison must be scheduled in advance.

The Missouri State Penitentiary overlooks the Missouri River and is a few blocks from the state Capitol. The facility, which opened in 1836, was the oldest continually operated prison west of the Mississippi River when it closed in 2004. Among its notable inmates were boxer Sonny Liston and bank robber Charles "Pretty Boy" Floyd. James Earl Ray had escaped from the prison when he assassinated civil rights leader Martin Luther King Jr. in 1968.

The prison was the site of a riot in 1954 that killed four inmates and injured 50 other prisoners. Four prison workers also were injured.