The 1956 race was the first to be governed by the United States Automobile Club. AAA withdrew from auto racing the previous August. Another change would have a more immediate effect on the current race. The track had been paved over with asphalt with only about 600 yards of the mainstretch still remaining brick.

The 1956 race is also known in Indy 500 lore as "Cagle's Miracle." Torrential rains pummeled the Speedway in the days leading up to the race. The track was full of standing water, access tunnels were completely flooded, and the infield was a muddy quagmire. The conditions threatened to postpone or outright cancel the race. Speedway superintendent Clarence Cagle supervised a massive cleanup effort, in which hundreds of thousands of gallons of water were pumped out of the tunnels and the infield. Cagle and his crew worked non-stop for 48 hours straight, some without sleep, and had the track ready just in time for race morning.

Time trials was scheduled for four days, but the third day was rained out. With the new surface, a new track record was expected. Pat Flaherty did not disappoint with a pole speed of 145.596 mph (234.314 km/h), over 4.5 mph (7.2 km/h) faster than the 1954 record. 29 drivers qualified opening weekend. The second weekend saw heavy rain that completely canceled Saturday and left only a small window on Sunday for 4 drivers to fill the field. Nino Farina was one of the drivers left out when he didn't get a chance to qualify his Bardahl-Ferrari.

The early part of the race turned into a three-man duel between Russo, O'Connor, and Flaherty. Russo was the first to retire when his tire failed and his car crashed and caught fire. At quarter distance due to yellows and the pit stops, Parsons took the lead followed by Freeland. By the 200-mile (320 km) mark Flaherty took over the lead followed by Freeland, Sweikert, and Parsons but Hanks was working his way through the fields after sustaining some damage in the Russo crash, eventually taking second. Flaherty had built up such a lead that he was able to make his last pit stop and remain in front. He crossed the finish line with Hanks the only other car on the lead lap. The only real change in the top cars toward the end was both O'Connor and Jim Rathmann having to drop back with mechanical problems while both drivers were in the top 5.

...
Wikipedia