Howard Aiken (9 March 1900 - 14 March 1973) built the Mark I, one of the first computers in the world.
Howard Aiken got his PhD in Physics at Harvard in 1939. While he was a graduate student at Harvard, he had a big problem: a set of differential equations whose solution was too tedious to be manually calculated. Undaunted, Aiken made plans to build a computing device adapted from Hollerith's punch card machines, but able to do calculations much more sophisticated than was possible in the "accounting machines" that were available then.
It took a lot of time and money, but Aiken was able to pull off a deal between Harvard and IBM to build this machine. In 1943, Aiken along with IBM's engineers put into operation the Automatic Sequence Controlled Calculator (ASCC), but which most people called the Mark I. The Mark I was an electromechanical machine, composed of switches that were controlled magnetically. Aiken would later build purely electrical machines.
The Mark I had 72 memory locations, and could add, subtract, multiply, and divide numbers with a precision of up to 23 significant figures. It weighed 35 tons. It was subsequently used for ballistic computations, a project in which Grace Hopper participated in.
Aiken has published papers on switching theory, electronics, and of course computer construction. He also developed the first acdemic program for computer science in the world. Aiken died on March 14, 1973 in St. Louis, Missouri
References:
http://kzoo.edu/~k98hj01/aiken.html
http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Aiken.html