http://www.columbiatribune.com/news/civil_war/years-ago-slaves-enlist-in-union-army/article_71e7ab70-538e-11e3-9929-001a4bcf6878.html
Slave enlistment in the Union army not only counted toward the Missouri enlistment quota of 13,516 men--exempting whites from conscription or enlistment--but each owner received $300 per slave enlisted, as compensation for the slave's freedom.