The circuit opened in 1950 on the former Hendricks Army Airfield and held its first race — a six-hour event — on New Year's Eve 1950. The 12-hour format was established the following year, and from 1953 to 1972 the race counted as a round of the FIA's premier sports car series, contested under names including the World Sportscar Championship and the International Championship for Makes.
During the 1950s Sebring stood as the most important American race for European factory teams, drawing drivers of the calibre of Juan Manuel Fangio, Alberto Ascari, Nino Farina, Stirling Moss, and Mike Hawthorn — at a time before the United States Formula One Grand Prix existed. The 1957 Sebring 12 Hours was the only American victory for five-time world champion Fangio.
The Sebring circuit combines former airport runways with narrow two-lane service roads, producing a notoriously bumpy and technically demanding surface. Combined with south-central Florida's perennial hot weather, the race is regarded as an excellent preparation for the 24 Hours of Le Mans, stressing mechanical reliability over an extended period. The circuit has been modified several times for safety, most significantly after the 1966 event, when five people died — the worst toll in the race's history — prompting a redesign that eliminated the Webster Turns and relocated the Warehouse Straight away from spectator areas.
Since those changes the fatality record has been far better for a circuit of Sebring's age and character. The track's unique layout, combining long straights with technical sections derived from wartime taxiways and perimeter roads, continues to define Sebring as one of the physically demanding events on the international calendar.
The race was a round of the World Sportscar Championship throughout the 1950s, 1960s, and into the early 1970s, before losing that status when the championship ended. It remained a top-tier North American event through subsequent decades, serving as a round of the IMSA GT Championship, the American Le Mans Series, and — for 2012 — a one-off opening round of the FIA World Endurance Championship before returning to ALMS for 2013.
Among the most celebrated partnerships in Sebring's modern history was Audi's dominance with the R8 prototype. Six overall victories were achieved by the Audi R8, placing it just short of the record seven wins held by the Porsche 935. Tom Kristensen won the race a record six times overall, in 1999, 2000, 2005, 2006, 2009, and 2012.
Notable individual editions include the 2006 race, in which the new Audi R10 TDI diesel prototype won on its first competitive appearance, and 2005, which saw the debut of the Chevrolet Corvette C6.R alongside the Aston Martin DBR9 in a hotly contested GT1 class battle. The 2020 race was rescheduled to November due to the pandemic, making it the only season in which Sebring was run twice; IMSA also held a shorter three-hour event at the circuit in July of that year to restart the season.
Races at Sebring up to 1969 began with the traditional Le Mans-style standing start, in which drivers ran across the track to their cars. This procedure was abolished following Jacky Ickx's protest at the 1969 24 Hours of Le Mans over the safety risks involved; 1970 marked the first Sebring 12 Hours to begin with a rolling start.
The race is known for beginning during the day and finishing under floodlights and darkness, contributing to its "once around the clock" reputation. Held in March, it consistently draws large manufacturer-backed entries and serves as an early-season bellwether for the IMSA championship and, historically, for teams preparing for Le Mans later in the summer.