- 1886 - While sources vary, Osceola was likely named a county in 1886. The boundary was formed from portions of Orange and Brevard Counties.
- 1899 - The Rivers and Harbors Act makes it illegal to dump refuse in navigable waters
- 1920s - The City Beautiful Movement was embraced by Kissimmee and St. Cloud civic leaders with construction of a wide landscape median on Main Street, as well as other civic beautification projects. Accelerated outward growth of Osceola County cities also occurred during the 20s.
- 1935 - First Florida Intergovernmental Planning Legislation was established
- 1940s - US Army Corps of Engineers build Kissimmee Airport.
- 1948 - Federal Water Pollution Control Act was approved, placing responsibility for controlling water pollution on the States and primarily focused on the treatment of sewage wastes