The land occupied by the Roosevelt Library was originally part of the extensive irrigated fields of Mission Concepcion which was re- established along the San Antonio River in 1731 from its original location in East Texas (along with two other missions located further to the south, Espada and San Juan Capistrano). The Concepcion acequia (irrigation ditch), which carried water from the river to the fields, is the oldest acequia in San Antonio. It was the Spanish acequias that allowed the five missions to flourish and to produce bountiful and varied crops. In 2010, a section of the Concepcion acequia was located 11 feet below the ground at the south end of the library property. It is probable that the adjoining section of the acequia lies beneath the entire eastern edge of the property.
Roosevelt Avenue was once the roadway to the San Antonio International Fair and Exposition which was held each October and November from 1893 to 1911. Col. Theodore Roosevelt and his Rough Riders trained at the fairgrounds in 1898 before departing for Cuba. The fairgrounds later became part of what is now Riverside Park, south of Roosevelt Park. Roosevelt became President in 1901, after President McKinley was assassinated, was re-elected in 1904, and held the office until 1909. Both the street and the park were named in his honor.