In the United States, the schoolhouse developed from simple log buildings built by the first pioneers to the typical wooden-sided, white-painted, one-room schoolhouses that could be found in profusion in the Midwest in the early twentieth century. The schoolhouse usually consisted of one classroom, windows on either one or two walls, a simple entrance on the front side and in rare cases added cloakrooms or a vestibule. Altogether more than 200,000 one-room schoolhouses were built in rural areas of the USA, mostly in the Midwest, where more than 90,000 of these simple buildings were erected. The Midwest had a rural population of approximately 17 million inhabitants in 1920. That means, at the beginning of the twentieth century, there was one schoolhouse for every 188 inhabitants in the Midwest. During the late 1930s and in the 1950s and 1960s, most of the one-room schoolhouses went out of use, owing to consolidations, demands for better education, and better means of transportation.