From Wikipedia (link below): Indianapolis businessman Carl G. Fisher first envisioned building the speedway in 1905 after assisting friends racing in France and seeing that Europe held the upper hand in automobile design and craftsmanship. Fisher began thinking of a better means of testing cars before delivering them to consumers. At the time, racing was just getting started on horse tracks and public roads. Fisher noticed how dangerous and ill-suited the makeshift courses were for racing and testing. He also argued that spectators did not get their money's worth, as they were only able to get a brief glimpse of cars speeding down a linear road.

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Construction of the track started in March 1909. Fisher had to quickly downsize his planned 3-mile (5 km) oval with a 2-mile (3 km) road course to a 2.5-mile (4.0 km) oval to leave room for the grandstands. Reshaping of the land for the speedway took 500 laborers, 300 mules, and a fleet of steam-powered machinery. Fisher and his partners began looking into the idea of paving the track with bricks or concrete. Paving in 1909 was still relatively new with only a few miles of public roads paved, leaving little knowledge of what would work best. Traction tests were conducted on bricks, proving they could hold up. Less than a month after the first car races, the repaving project began. Five Indiana manufacturers supplied 3.2 million 10-pound (4.5 kg) bricks to the track. Each was hand laid over a 2-inch (51 mm) cushion of sand, then leveled and the gaps filled with mortar. At the same time, a concrete wall 33 inches (840 mm) tall was constructed in front of the main grandstand and around all four corners to protect spectators. The final brick added to the track was made of gold and laid in a special ceremony by Governor Thomas R. Marshall. Before the work was completed, locals nicknamed the track The Brickyard. Today, 3 feet (0.91 m), or one yard, of original bricks remain exposed at the start-finish line.