This report documents the procedures used to delineate 382 labor market areas (geographic areas encompassing both the place of work and the place of residence of a local population) for the United States. The data used to delineate these labor market areas (LMA's) were the 1980 Census journey-to-work data for counties and county-equivalents in the 50 States and the District of Columbia. Matrices of these data were constructed to indicate the relative strength of the commuting ties between each pair of counties. The results of a hierarchical cluster analysis on these matrices were then used to identify groups of counties with strong shared commuting ties.