The 1960 census, conducted as of April 1, 1960, marked the first mailout of the decennial census as the primary means of collection of household's census data. The postal service delivered questionnaires to every occupied housing unit and householders were asked to complete the questionnaire and hold it for an enumerator to pick up.
Data processing for the 1960 (and later) censuses improved through the use of the Census Bureau's "film optical sensing device for input to computers" (FOSDIC). The 1960 questionnaires were designed so that respondents could indicate their answers by marking small corresponding circles on the page. When the completed questionnaires were photographed onto microfilm with automatic cameras, the shaded circles appeared as dots. The FOSDIC read the microfilm and transferred the data each dot represented to computer tape for processing.
Upon completion of the 1960 census, the U.S. resident population totalled 179,323,175, an 18.5 percent increase from the 1950 census.