Mechanized clearing of large tracts of forested land left numerous scrub piles behind. Fewer people farming more land meant numerous abandoned farm buildings. Raccoons need a rich variety of both plant and animal food in their diets. They normally select invertebrates such as snails and insects, bird eggs, small birds and mammals, and supplement their diets with wild fruits and nuts. But raccoons could not survive in pothole country with this natural diet alone.
Man provides the rest.
The arrival of the combine on the farm scene increased the available food. Combines, though able to harvest large areas in a short time, leave waste grain on the ground. Rapid increases in grain harvests meant excesses stored in buildings easily accessible to raccoons. They quickly adapted to scrounging grain which became a staple item in their diet. Some wildlife experts believe another phenomenon, the wholesale eradication of coyotes and wolves by man during the 40's and 50's, may have reduced predation pressure on raccoons and opened a new niche in nature's balance.