Think the first MO Trout Hatchery was in Aurora, MO and it was private, post civil war era. The US Fish Commission was formed in that era as well and they got into the business of distributing trout and “pacific salmon” all over the place. Some lived, some did not. Not sure how long Neosho has been in business, but 1890-1920 seems about right. 1940’s pre WW2 CCC buildings are abundant around the trout parks, so something was there before.