In 1940, there were 17,500 movie theaters in the United States -- one for every 8,000 people. Films debuted in the "first-run market", those 1,360 theaters in the largest cities in the U.S. and Canada (those with more than 12,500 people). The first-run market generated half of a picture's income. The most important theaters were the 450 deluxe movie palaces in 95 cities with a population of more than 100,000. The movie palaces played 24 hours a day, and generated the lion's share of the first-run market.
Studios engaged in a "run-zone-clearance" system. A film would run in the first-run zone, and then the the theater might stand empty for a short period of time ("clearance") until the next film arrived. Typically, a film would run in the largest cities, then move to the suburbs, then to the smaller cities, then to rural areas. Because of run-zone-clearance, a picture could take six months before being pulled from distribution. Average daily attendance in movie theaters was 500, with the average show attendance just 250.
Average figures are meaningless, however. Theaters varied widely in size and movie-going attendance rates.
But consider: In its first five weeks at Radio City Music Hall, "Rebecca" played to 750,000 people. That's 20,000 PER DAY.