As the only maximum-security prison in the state, the Oregon State Penitentiary (OSP) has housed some of the most violent criminals on the West Coast, including brutal serial killers Charley Panzram in 1915 and Jerry Brudos in 1969. Sixty men have been executed inside OSP. The prison was originally built in Portland in 1851 but moved to Salem 15 years later, after Oregon became a state. From that time forward, the Oregon State Penitentiary grew from 23 prisoners in 1866 to 1,912 by 1992. The penitentiary suffered several serious fires and riots. On March 9, 1968, the most expensive riot ever experienced in the United States flared inside the walls, causing over 2.5 million in damages. Numerous escapes plagued the prison until 1970, when security measures were tightened. The most famous escape involved Harry Tracy and David Merrill in 1902.