How many acres would you need to build a one mile oval racetrack?

It depends on what the purpose of the kind of racing is proposed to be run on the track. A road course, which there aren't very many NASCAR racews run at requires the largest amount of land. This is the only kind of track were a driver actually turns right. Next, is the super speed ways like Daytona or Atlanta. Then you got "The Mile" tracks like Dover. Then there are the short tracks like Richmond or Darlington.

What makes the track size so interesting is the specific strategies associated not only with the tracks size, but also the shape and surface.

Finally, the amount of land needed must also take into account the size of the space necessary to safely support the crowd of the venue's events.