The Isis opened on North Main Street on May 21, 1914, the first theater on Fort Worth's north side, near the stockyards. The North Side Amusement Company built it, and the original house was small, about 18 by 61 feet, with silent films shown from a hand-cranked projector in a booth tacked onto the back. L. C. Tidball, who later said he meant to run the theater for a few months for fun, took it over within a few years and was its owner and operator for more than half a century.
Fire destroyed the building in 1935. The theater was rebuilt on a larger lot, and the New Isis opened on March 27, 1936, with a "Hollywood Premiere." Ginger Rogers was invited and instead spoke to the packed house by telephone, and the feature was her film In Person. The Moderne building had a white stucco front, an enameled blue-and-red canopy, a tall "New ISIS" blade sign in neon, one of the largest screens in Fort Worth, washed-air cooling and hearing units for patrons with poor hearing. Under segregation, three rows at the back of the mezzanine were set aside for Black patrons.
Marine Creek flooded the theater in April 1942, with water five feet deep inside. Around 1954 or 1955 the Isis was refitted for CinemaScope, magnetic sound and 3D films, but kept its 1936 projector stand and carbon-arc lamps. Harold James Griffith, from an Oklahoma City family of theater operators, bought it from Tidball in 1970. Like many neighborhood houses, the New Isis lost its audience to larger multiplexes and closed in 1988.
The empty building stood for decades in the Fort Worth Stockyards Historic District. A 2018 amendment to the district's National Register listing recognized the New Isis as a contributing building and an excellent local example of a Moderne movie theater, noting that the original projection equipment and the 18-by-36-foot screen were still in place. A new owner bought it that spring, and it reopened as the Downtown Cowtown at the Isis on May 28, 2021, with western movies and live shows planned. It closed again on November 26, 2023.