1866 - Springfield City Railway Co. introduces horse car service on North 5th St. route.
1867 - Capital Railway introduces horse car service on east Monroe St. route.
1871 - Capital Railway consolidated into Springfield City Railway Co.
1879 - Citizens Street Railway Co. introduces horse car service on North 9th St. and South 2nd St. routes. Additional routes opened on South 11th St. and on Rutledge St.
1889 - People's Gas Motor & Horse Railway introduces horse car service on South Grand route on city's southwest side, and on North 11th St. connecting with Citizens Street Railway Co. North 9th St. route.
1893 - Springfield City Railway Co. and People's Electric Railway acquired by Springfield Consolidated Railway Co., which electrifies routes.
1909 - Union Railway Gas & Electric Co. incorporated, acquires Springfield Consolidated Railway Co. as a subsidiary.
1913 - Commonwealth Power Railway & Light Co. acquires Union Railway Gas & Electric Co. as a subsidiary.
1921 - Springfield Consolidated Railway Co. reorganized as Illinois Power Co., including electric utility. Shortly after, first bus route is introduced.
1922 - Commonwealth Power Co. incorporated as subsidiary of Commonwealth Power Railway & Light Co., controlling Illinois Power Co.
1929 - Commonwealth Power Co. merged into newly incorporated Commonwealth & Southern Corp., with Illinois Power Co. as a subsidiary.
1933 - Illinois Power Co. reorganized, with electric utility transferred to Commonwealth & Southern Corp. subsidiary Central Illinois Light Co. Transit system transferred to newly formed Springfield Transportation Co., a subsidiary of Commonwealth & Southern Corp. subsidiary Transportation Securities Corp.
1937 - Last local streetcar service replaced with buses.
1943 - Transportation Securities Corp. dissolved, Springfield Transportation Co. sold.
1945 - United Transit Co. incorporated, which would acquire Springfield Transportation Co.
1962 - United Transit Co. acquired by American Transportation Enterprises (ATE).
1968 - Springfield Transportation Co. becomes publicly owned Springfield Mass Transit District.
2016 - Springfield Mass Transit District renamed Sangamon Mass Transit District, reflecting the expansion of services into additional areas of Sangamon County.