The milk production segment of the U.S. dairy industry has experienced significant change over the past two decades. Various USDA data sources allow for analysis of how dairy farms have changed in structure and production costs. This study uses USDA’s Agricultural Resource Management Survey (ARMS) dairy version data from 2000, 2005, 2010, 2016, and 2021 (and other USDA data) to examine changes in farm structure, production costs, and technology adoption and to compare dairy farms by size and production region over the past two decades. Methods used to analyze the data include the difference in means tests and stochastic frontier analysis. Dairy farm numbers have decreased, while milk production has increased; increases in the use of some advanced farm technology have occurred; larger farms benefit from economies of scale and are the greater users of advanced technologies and production systems; and there are regional differences in farm structure and cost of production.