At the far west end, beyond the state and foreign pavilions, the exposition laid out a mile racetrack on Presidio land. Inside it were a polo field, a military drill ground and an athletic field. The ground had been soft, swampy flat at the foot of the hills, and it was filled and raised to grade by dredging, part of 114 acres of Presidio land the exposition reclaimed. Serpentine rock quarried in the Presidio surfaced the track and drill ground.
Three grandstands for more than 25,000 people lined the straightaway. Under one of them was a cooling shed for polo ponies, and there were more sheds for race horses and quarters for athletes. The exposition "Stadium" was a portion of the drill ground in the west half of the track, fitted with jumping pits, a running track of three laps to the mile and, once the polo was over, a quarter-mile straightaway across part of the polo field. It opened on April 9, 1915, with the Pacific Coast Interscholastic meet, which Lowell High School won.
The season's program filled it. There was a polo tournament from March 15 to May 1, two harness meetings (June 5–19 and October 30–November 13) with four $20,000 stakes, cavalry and mounted military contests, dog field trials in the polo field, and in August the national A.A.U. championships, which drew stars like Ted Meredith, Hannes Kolehmainen and Norman Taber. The field was also used for flying, and the Overfair Railway and the exposition's main rail line both ran out to it.