The Saint Louis Exposition or St. Louis Expo was a series of annual agricultural and technical fairs held in St. Louis' Fairgrounds Park, from the 1850s to 1902. In 1904, the Louisiana Purchase Exposition, a major World's Fair, was held in St. Louis, Missouri, United States. The annual agricultural/technical exposition was not held in 1903-4, and ceased after the World's Fair. It is easy to confuse memorabilia from the annual St. Louis Expositions with 1904 World's Fair memorabilia.
In 1855 a group of St. Louisans founded the "St. Louis Agricultural and Mechanical Association," which held annual fairs starting in 1856. Prominent citizens founded the association, which was not intended to pay dividends. All profits were to expand and beautify the fairgrounds.
A site of 50 acres (200,000 m2) at the northwest corner of Grand Avenue and the Natural Bridge Plank Road was purchased by the Association. It was well outside the city limits—an hour's journey from the city by horse-drawn carriage. The largest amphitheater in America was built, seating over 12,000 plus standing room.
The annual fair was an immediate success and soon became noted all over the country. It was, in reality, a gigantic county fair. There were booths for vending wine, beer, and other delicacies. There were displays of livestock, poultry, vegetables, grains, and the latest inventions in farm machinery, tools, household gadgets, etc.
Buildings for the fair included the amphitheater, mechanical hall and agricultural hall. Additional structures were floral hall, the Gothic fine arts hall, and the wire gallinarium, a three story "Chicken Palace" for displaying poultry. In addition to the exposition halls, a racecourse, grandstand and jockey club were built.
In 1860, the grounds were made available to the public for picnics for a nominal fee, but the Fairs were soon interrupted during the Civil War for a few years, when the fairgrounds were used for military and training purposes. The large amphitheater was converted into one of the "largest, most thoroughly ventilated hospitals in the United States" accommodating 2,500 patients. Numerous other fairgrounds buildings of the association were taken over for officer’s quarters, medical dispensaries, kitchens, and other military purposes. After the war, the park was returned to its former use by the Association.
A zoological garden was added in 1876 modeled after the finest European zoological buildings, and consisting of a monkey house, bear pits, and carnivore house. Later additions were an aviary, outdoor pens for herbivorous animals, a lake and a grotto. These structures and facilities were eventually absorbed by the St. Louis Zoo following its establishment.