The Pittsburgh, Cincinnati, Chicago and St. Louis Railroad was built through the area in 1867. Around 1869, a half-mile long switch was built to haul wood to a train refueling station. This switch would become the nucleus of the town. Railroadmen began calling it "Switch" and soon thereafter, the area was known as "Switzer" and then "Sweetser".
The original plat of town of Sweetser was entered on October 14, 1871 by Lanford Prater, John Hubert, James H. Vinson, Urich Mars and H.B. Bragg with the Grant County Recorder's office. The land which formed the original plat of Sweetser had been entered in the District Land Office in Fort Wayne, Indiana on May 22, 1848 by Samuel Blinn. Additional plats to the town were Nuzum's in 1873, and the Wilcut's, McGee's, Bishop's and Nuzum's 2nd, all platted in 1874.
The early business section was north of the railroad on the west side of Main street. A saw mill was located at what is now the present site of the Methodist church (413 N. Main). Sweetser had several dry goods stores, a blacksmith shop, a jeweler and a saloon.
When natural gas was struck around Sweetser in 1885, the town was ready for development. The Brickner Window Glass Company, established in 1893, attracted many people not only living nearby but from other states to come to work and live here. The glass factory was located on the west side of town, being situated just west of what is now 319 W. Hubert Street. The factory was also known as Schick & Hawkins Window Glass Company.
From 1884 to 1894 there were five additions platted to Sweetser, namely Thompson's, Sherron's, Sherron's 2nd, Sherron's 3rd and Hawkins.
A hotel, known as the Vardaman Hotel, was located at 103 Main Street in lots number 27-29 of the original plat. This hotel was built to accommodate the number of persons working at the glass factory.
The Friermood Tile Factory was started in 1888 and was located at the end of Walnut Street. It made tile for draining the lands around Sweetser into Pipe Creek.
In 1901, a new railroad was established in Sweetser, the C & O, which was parallel with the Pensylvania railroad tracks. Between 1915 and 1925, eight passenger trains stopped in Sweetser. With the use of the automobile, passenger service began to fall off. Passenger service was stopped at the Sweetser depot of the Pennsylvania Railroad, now Penn Central in 1947 and the C & O in 1953.
In 1921, street lights were turned on in town for the first time and in 1922, the Community Hall was completed, which contained an auditorium and stage as well as a hardwood floor for basketball. In 1926, Main street was first paved through downtown Sweetser.
The Sweetser News Exchange, a weekly paper, began publication in 1932 and continued through several publishers until ceasing in 1958.
The Sweetser Lions Club was started in 1945 and continues to be active today. In 1950, a group of citizens organized the Sweetser Volunteer Fire Department, Inc., which served Sweetser and Pleasant Township.
In 1957, the Sweetser schools joined together with Richland and Jackson Townships to form Oak Hill School. In 1965, Sims and part of Franklin Township joined to make the Oak Hill United School Corporation.