Many changes in historical housing practices and demographics may be surprising to people looking at the current housing situation and may help us understand the sort of changes that have occurred and the speed at which significant change is possible. Beginning in 1940, the decennial census survey started asking questions about the housing stock in the United States. By examining the questions and answers, we can see how housing has changed in the past 60 years.The art and practice of indoor plumbing took nearly a century to develop, starting in about the 1840s. In 1940 nearly half of houses lacked hot piped water, a bathtub or shower, or a flush toilet. Over a third of houses didn't have a flush toilet. As late as 1960, over 25% of the houses in 16 states didn't have complete plumbing facilities.Half of all households heated with coal in 1940, and another quarter heated with wood. By 2000 the fraction of houses that heated with wood or coal was below 5%. By 1960, fuel oil and natural gas were the primary heating fuels. The number of houses that used fuel oil peaked that year and has declined in national importance ever since. The use of electricity as a heating fuel has climbed while fuel oil has declined. These changes in choice of main heating fuel coincide with an expansion of the population in the West and South, helped by the advent of airconditioning.Another significant change has been the number of people per household and the size of housing units. The average number of people per household has declined while at the same time new houses are getting bigger and have more rooms.In 1900 the average household was over 4.5 people, in 1940 it was about 3.5, and by 1990 it had declined to less than 2.5. In 1940, the percent of households consisting of people living alone was less than 10%, since 1990 over a quarter of households have been single-person.At the same time new houses have been getting larger. Over the past 15 years the median floor area of new homes has increased 25%. A quarter of new homes now have 4 bedrooms, up from just over 10% 25 years ago. Now 80% of new homes have 2 or more bathrooms, compared to half of new homes with only one bathroom in 1975. During the past quarter century, when the housing stock was changing so much, surveys of the overall happiness of the American population show no increase and possibly even a decline.Looking at these long-term, large scale changes can remind us that the housing stock is dynamic and may help us better understand what influences it.