The Food Stamp Program, piloted in Rochester, New York, soon extended to five additional counties in Ohio, Washington, Alabama, Oklahoma, and Iowa. At its peak, the Food Stamp Program was available in 1,741 counties in the U.S., encompassing nearly two-thirds of the U.S. population. While eligibility standards varied from county to county, the number of enrolled Americans reached 4 million by May 1941. The impacts were particularly profound in urban locations where, by one estimate, food stamps comprised as much as 4% of total food sales.