I have to admit that I’m horrible with anniversaries and birthdays. Remembering specific dates for important events have never been in my wheelhouse. Despite that, intuition struck that this year’s Formula One race in Austin is an important one. One might think it would be as easy to verify as counting every F1 race that has taken place in the United States, but not every race here was billed as the national grand prix. For example, the races in Dallas, Detroit, Las Vegas and Long Beach were never officially called the United States Grand Prix.

Race program covers were the first place I went to search through. The goal was to find the most recent U.S. Grand Prix which advertised itself with an edition number, then I could simply count each race back to the present. The most recent program ended up being for the last Formula One race at Watkins Glen, which billed itself as “22nd Toyota Grand Prix of the United States.” When the U.S. Grand Prix returned as a race moniker for the 1989 F1 race in Phoenix, AZ, Formula One had transitioned to standardized race program covers.

The uniform cover designs still used today have almost entirely erased mentioning which edition of the race is taking place, except for Monaco. The principality’s race is allowed to slightly deviate from the season’s standard design and always mentions the race’s edition. By this counting method, this Sunday’s race in Austin is the 42nd United States Grand Prix.

Though, I discovered an issue by counting events this way. A U.S. Grand Prix was seemingly omitted over time. The 1975 edition of the race is billed on the program as the 18th running. Then after a two-year deviation in design, the 1978 edition of the race is billed as the 20th running, not the 21st. There are two plausible explanations for this change.

First, the Sports Car Club of America (SCCA), the race organizing body, could have removed the inaugural edition of the event in 1958 because the race was run to sports car regulations. The 1952 Monaco Grand Prix was also run to sports car regulation but is still included in the race’s official lineage, providing reasoning either against this explanation or a basis to reverse it.

Second, the SCCA might have removed the same event because it was sanctioned by the United States Auto Club (USAC). However, numerous long-running F1 races have had different sanctioning bodies across their histories while maintaining the same lineages, such as the French and German Grands Prix. This correction makes this weekend’s event the 43rd United States Grand Prix.

Including races from other sanctioning bodies also means adding a few other races that were also excluded, specifically the American Grand Prize. The race was organized by the Automobile Club of America in the style of the French Grand Prix. The ACA was a body formed as a sister organization in the United States in association with the Automobile Club de France. The Grand Prize was run seven times before the event ceased due to the entry of the United States into World War I. This inclusion makes this Sunday’s race in Austin the 50th United States Grand Prix.

While this exercise might seem completely arbitrary and insignificant, it is an important aspect of following how much Grand Prix racing’s popularity and influence within the United States has fluctuated over the decades.