Buick's first competition was in 1904, a local dealer in NY/NJ entered a
stripped down 2cyl Buick in a hill climb and beat the previous best time by
50%. In 1905 Buick won its class in the Glidden Tour, a 1,000 mile run
which included a timed ascent up Mount Washington. After a year or so of
dealer participation, Durant saw the advantages of running a factory team.
They were very successful and included Bob Burman and Louis Chevrolet as
their most successful drivers. Other drivers included Arthur and Gaston
Chevrolet, Lewis Strang, Hugh Easter, George DeWitt and Louis Nikrent.
BTW, IMS opened August 1909 and Buick showed up with an entry of 15 cars! Of
course there were a series of shorter races for cars with smaller
displacement. There was no 500 mile race that year.
IMHO, the most famous early Buick race car was the 1910 Buick Bug. I
believe there were two of them built. Very impressive with sloped, pointed
nose and a surface-mounted fin-coil radiator wrapping around the cowling. I
recently saw the remaining Buick Bug at the Buick Gallery and Research
Center in Dearborn. BTW, they were 4cyl, 622cid!!