Before 1971, the Watkins Glen circuit measured 2.350 miles (3.782 km) on the original Grand Prix Race Course layout that had been in use since 1956. The track underwent its most significant structural change in preparation for the 1971 Formula One season. Engineers added a new four-turn complex departing from the southern end of the backstretch: after the Loop-Chute section, cars swept left downhill through the woods along the edge of the hillside, then turned right twice in quick succession before cresting a blind summit and returning via a final left-hander to the old circuit.
The four-corner complex received the nickname "the Boot" — or sometimes "the Anvil" — because of the shape it created when viewed on a track map. The new segment extended the circuit to 3.377 miles (5.435 km). The pit lane and start/finish line were simultaneously relocated to a new straight ahead of the northwestern right-angle corner known as The 90.
The Boot was not completed in time for the 1971 Six Hours of Watkins Glen sports car race, which ran instead on the shorter incomplete layout. All facility improvements were finalised for the 1971 United States Grand Prix in October.
With the Boot in place, Watkins Glen hosted the United States Grand Prix for ten consecutive seasons, from 1971 through 1980. The circuit was popular with teams and drivers: the race typically paid the highest starting money and prize money on the entire Formula One calendar, and the autumn timing amid the Finger Lakes' fall colours made it a fan favourite.
French driver Francois Cevert, a previous winner at the Glen, died in a crash during practice for the 1973 United States Grand Prix. Course officials responded by installing a fast right-left chicane through the Esses section in 1975, named the Scheckter Chicane, which was subsequently removed in 1985 when the circuit reopened under new ownership.
The track's association with Formula One ended after the 1980 race, won by Alan Jones for Williams. In May 1981 the International Auto Sports Federation removed the event from the calendar after the circuit defaulted on an 800,000 dollar debt to the teams.
Following bankruptcy in 1981 and a period of disuse, Corning Enterprises partnered with International Speedway Corporation to purchase and reopen the track as Watkins Glen International in 1983. The reopened circuit operated initially without the Boot section for major events; NASCAR returned in 1986 using the short 1971 course, and IMSA also migrated to the shorter layout through the 1990s.
The Boot section, seeing relatively little use in the interim years, was repaved and upgraded in the mid-2000s as part of broader facility improvements. When IndyCar returned to Watkins Glen in 2005, the series used the full Boot layout and continued to do so through the 2010 and 2016 seasons. The full Grand Prix Course also received a complete resurfacing in 2015 as part of a track-wide repave funded partly by a New York State grant.
The question of whether NASCAR's Cup Series should switch from the short course to the full Boot layout has been an ongoing discussion. As of the mid-2020s, NASCAR continues to use the shorter configuration despite periodic consideration of adopting the longer Grand Prix Circuit.
The Boot section defines the character of the long course. From the Loop-Chute, a blind entry sweep drops cars downhill through the treeline on a fast left-hander. The subsequent right-hand turns climb back up the hillside, with the blind crest before Turn 9 particularly demanding: drivers commit to the uphill right-hander without a clear view of what lies beyond the summit, a feature frequently cited alongside the Raidillon at Spa as one of motorsport's great blind-commitment moments. The layout rewards drivers who carry speed through the downhill left and balance the car for the steep climb.
The Inner Loop chicane, added in 1992 at the back straight to address a series of serious accidents including the death of NASCAR driver J. D. McDuffie in 1991, slightly increased the lap distance and broke up what had been a high-speed approach to the Boot entry.
As the permanent home of the United States Grand Prix through the 1970s and a venue that has hosted Formula One, sports car endurance racing, IndyCar, and Can-Am, the Boot layout carries a depth of historical association that places Watkins Glen among the iconic American road courses.