The town of Sidney was laid out in 1851 on land owned by Judge Thomas Greenwood. J.J. Singleton opened a store and S.T. Cromwell built and operated the first hotel in the same year.
Founded shortly after the discovery of gold in California, Sidney became a popular stopping place for travelers who were lured West by the great gold rushes of the 1850s. It was also named the county seat in 1851, at which time the first courthouse was built.
By 1863, the courthouse was in need of repair and there were discussions about moving the courthouse to another town. Soon after that, the old courthouse burned to the ground. However it was decided to build another in Sidney in 1889.
Originally named Dayton, the surveyors who laid out the town boarded with the family of Milton Richards. At the suggestion of his wife, Jane, a native of Sidney, Ohio, they recommended the name of Sidney for the town.
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.