1893 - Streetcar route extended east of Hammond into East Chicago, and north into Whiting. Hammond Electric Railway Co. acquired by Hammond Whiting & East Chicago Electric Railway Co.
1894 - Streetcar route extended northwest of Whiting to state line, connecting with streetcars operated in Chicago by South Chicago City Railway Co.
1895 - Streetcar route extended north of Hammond to Whiting via Sheffield Avenue, connecting with route from East Chicago.
1896 - Hammond Whiting & East Chicago Electric Railway Co. acquired as subsidiary of South Chicago City Railway Co. Joint through streetcar service introduced to 63rd Street on Chicago's south side from both Hammond and East Chicago. The Hammond route would be identified as Route 11, while the East Chicago route would be identified as Route 12.
1899 - Streetcar route extended on Conkey Street south of Hammond, serving new Conkey Co. factory.
1903 - Chicago & Indiana Air Line Railway introduces streetcar service between Indiana Harbor and East Chicago. The following year, the company would be renamed the Chicago Lake Shore & South Bend Railway, evolving to the Chicago South Shore & South Bend Railroad interurban line, now the Northern Indiana Commuter Transportation District.
1909 - Gary & Interurban Railway introduces service on Sibley in Hammond. The following year, this line would be completed from Gary. This line would be operated separately, as part of what eventually would be known as Gary Railways.
1910 - Hammond Whiting & East Chicago Electric Railway Co. sold to Hammond Whiting & East Chicago Railway Co.
1913 - Streetcar route completed to Indiana Harbor. This was a joint double track line, with one track owned each by Hammond Whiting & East Chicago Railway Co., and Gary & Interurban Railroad. The Hammond Whiting & East Chicago Railway Co. route between Hammond and Indiana Harbor would be identified as Route 10. While the Gary & Interurban Railroad, which eventually would become Gary Railways, operated a route to Indiana Harbor from Gary.
1921 - Midwest Motor Coach Co. begins operating competing bus service between Gary and 63rd Street, also competing with jitneys which had operated over route since World War I. By 1925, Midwest Motor Coach Co. emerged as the only operator of buses over the route.
1925 - Several bus companies introduce local bus service in Hammond, Whiting, and East Chicago.
1926 - Midland Utilities, a public utility holding company controlled by Samuel Insull, forms subsidiary Shore Line Motor Coach Co., providing additional competing bus service between Gary and 63rd Street, and extending east of Gary to points in Michigan. Shore Line Motor Coach Co. would eventually acquire all bus routes in Hammond, Whiting, and East Chicago area, except for Midwest Motor Coach Co.
1929 - Hammond Whiting & East Chicago Railway Co. sold to Calumet Railways, Inc., which had minority control by Midland Utilities. Midland Utilities becomes a subsidiary of Midland United Co., controlled by Samuel Insull, and also acquires Midwest Motor Coach Co.
1931 - Chicago & Calumet District Transit Co. formed, and acquires Calumet Railways, Inc., Shore Line Motor Coach Co., and Midwest Motor Coach Co. Shore Line Motor Coach Co. service east of Gary had been sold in 1927.
1932 - Chicago & Calumet District Transit Co. acquires control of Gary Railways, continuing to operate it as a separate company. Streetcar service south of downtown Hammond to Conkey Street discontinued.
1934 - Chicago & Calumet District Transit Co. discontinues streetcar service to Indiana Harbor. Gary Railways service to Indiana Harbor would continue until 1939.
1940 - Streetcars discontinued on two remaining routes. Chicago & Calumet District Transit Co. bus service continued to exist to 63rd Street.
1941 - Chicago & Calumet District Transit Co. introduces commuter express bus service into downtown Chicago.
1943 - Gary Railways Co. sold to Gary Railways, Inc.
1946 - Gary Railways streetcar route into Hammond replaced with buses.
1951 - American Transit Corp. incorporated, which within a few years would acquire Chicago & Calumet District Transit Co. as a subsidiary.
1956 - Chicago South Shore & South Bend Railroad opens new bypass route through Hammond and East Chicago, paralleling newly constructed Indiana Toll Road.
1971 - Chicago & Calumet District Transit Co. discontinues local service in Hammond and East Chicago, leaving those cities with no transit service for a period of time.
1972 - Shore Line Bus Co. attempts to operate local service in Hammond and East Chicago, but discontinues service after a few months.
1973 - Chicago & Calumet District Transit Co. discontinues Chicago-Gary bus service.
1973 - East Chicago Transit begins operations, with free fare.
1974 - Chicago & Calumet District Transit Co. merged into Chicago Gray Line, also owned by American Transit Corp.
1976 - Hammond Transit System begins operations, operated under contract by Gary Public Transportation Corporation.
1980's - Chicago Gray Line bus service into downtown Chicago sold to Hammond Yellow Coach Lines.
1983 - Hammond Yellow Coach Lines begins operating Hammond Transit System under contract, as operation by Gary Public Transportation Corporation outside Gary city limits was determined to be illegal.
1989 - Hammond Yellow Coach Lines ceases operations, with no replacement for downtown Chicago service, as downtown service had lost ridership due to company unreliability. Hammond Transit System contract assumed by ATC/Vancom, ironically a successor to American Transit Corp. Contract later assumed by Progressive Transit
2003 - Progressive Transit acquired by First Transit.
2010 - Hammond Transit System operations transferred to new Regional Bus Authority.
2012 - Regional Bus Authority ceases operations after running out of money.
2014 - Gary Public Transportation Corporation introduces circulator bus route in Hammond and Munster, as a connection to its own route between Gary and Hammond.