The Town of Sidney was started by three commissioners hired by the State of Iowa to find a central location in the county for the establishment of a county government. In 1851 land was purchased from Mr. and Mrs. Milton Richards, with Mrs. Richards naming the new town Sidney, after her home town of Sidney, Ohio. The first Courthouse was built at that time, a small wood building. It was not only used for county business, but also served as the first City Hall. S.T. Cromwell purchased the first lot sold in Sidney, Lot 5 of Block E, where he built and operated the first hotel.
By 1858 the first courthouse was too small, so a brick one was built. In 1863 there was an attempt to blow up this courthouse, creating much damage and costing the county $2000 for repairs. In 1888, an unknown person set the building on fire, destroying it completely. The present day courthouse was built in 1889.
Today, Sidney has a library, several churches, athletic field and swimming pool built in 1961 at the scenic city park.
The town is host to the Fremont County Fair and the Sidney Iowa Championship Rodeo, which is the world's largest continuous outdoor rodeo.
The rodeo was started in 1924 as soldiers returned from World War I to renew interest in the annual Grand Army of the Republic reunion. The American Legion Post No. 128 continues to operate the rodeo. In Sidney's early days, it also hosted chautauquas and old settlers picnics.
The Fremont County Historical Society started an historical museum in 1972 on the east side of the square. Items range from carriages and farm equipment to antique bedroom sets and dishes.
The front lobby houses a prehistoric display with adjacent Indian room, pioneer room and library. Rooms have also been decorated to portray an old-time kitchen, bedroom, parlor and general store.
At one time, Sidney businesses included six dry goods stores, three drug stores, six grocery stores, one bank, three blacksmith shops, a wagon and carriage factory, one tailor shop, a barbershop, four physicians, eight lawyers as well as bakeries, print shops, saloons and a chair factory.