Air is free. Horsepower costs money.
That phrase was coined in the 1960s when race-car design was much less restricted than it is today, and when race-car aerodynamics were not well understood. 
The greatest innovator in sports-car racing was Jim Hall, who built his Chaparrals in Midland, Texas, with an open line to General Motors in Detroit. His 1966 CanAm series entry, the Chaparral 2E, featured the first adjustable, suspension-mounted wing. Similar wings became universal in CanAm and Formula One before being banned in 1969 after several F-1 wings collapsed at speed.
Just about the time the high wings went away, GM engineers Don Cox and Don Gates turned their attention from the air above the car to the air under it. Gates went to work for Hall in 1969 and brought the basic hardware with him that would be developed into the Chaparral 2J, the Sucker Car, which introduced ground effects to race car design.
Its racing record was unimpressive. It appeared for only four CanAm races during the 1970 season and never led a lap. But it won three pole positions by almost ridiculous margins and generated world-class levels of both interest and controversy.
The 2J wasn’t handsome. It was plain white, blunt-nosed and slab-sided. Its secret was in the rear-engine bay, which contained not only a big-block aluminum Chevy, but a modified Rockwell JLO snowmobile engine driving two exhaust fans by belts. The underside was sealed by sliding Lexan skirts, so the exhaust fans literally sucked the air out from under the car, creating far more downforce than a wing, at any speed, and without the drag penalty.
After a spring full of rumors, the car appeared at the July 1970 Watkins Glen CanAm, with world champion Jackie Stewart driving on a one-race deal. Stewart qualified third and ran there for 15 laps, but the track was breaking up on several corners and the debris sucked up damaged the fan motor and the drive belts.
The Sucker Car made three more appearances, each with Vic Elford driving. It won all three poles, each by a margin of one full second or more, but suffered fan motor trouble at Road Atlanta and Riverside and blew its main engine in race morning warm-up at Laguna Seca.
The exhaust fans were ruled to be illegal “movable aerodynamic devices” and the Chaparral 2J was never to race again.  
Almost a decade later, that other great innovator, Colin Chapman, achieved ground effects legally and more simply by using underbody venturi tunnels on the Lotus 78 driven by Mario Andretti. One of the first to adopt Chapman’s system was Jim Hall on his Chaparral 2K Indy car — the last of the Chaparrals, which Johnny Rutherford drove to victory in the 1980 Indianapolis 500.