Before we had electronic devices to do scientific computation, lengthy calculations were done by large groups of human computers. These individuals were usually intelligent persons who were unable to pursue a career in science because of their social or economic standing. They are best characterized as "blue collar mathematicians." Several of the human computers, notably the staff at the U. S. Nautical Almanac, the workers at George Snedecor's Statistical Laboratory and the members of the WPA Mathematical Tables Project, made many small contributions to the development of numerical analysis. The Mathematical Tables Project, which was probably the largest computing group of modern time with over 450 computers at its prime, became the basis for the Institute for Numerical Analysis at UCLA and the Applied Mathematics Laboratory at the National Bureau of Standards. This talk is based on a new book, which is being published by Princeton University Press.