Margaret K. Butler, a mathematician who helped develop U.S. computers in the early 1950s and championed women in science, has died, friends said. Butler, the first female fellow at the American Nuclear Society and director of the National Energy Software Center at Argonne from 1972-91, was 88, the Chicago Tribune reported Tuesday. Butler was remembered not only for her science contribution but for her unstinting efforts to improve opportunities for women in science. "She made her mark, but she also brought along and helped create the careers of many women in computers," Joseph Cook, a retired senior scientist at Argonne who worked with Butler on several projects, said. "When Margaret got ahead, she hired other women, and when warranted, she'd recommend them for higher positions." Born in Evansville, Ind., Butler attended Indiana University in Bloomington on a scholarship, discovering a passion for mathematical statistics and differential calculus. After a stint with the U.S. Army Air Forces as a civilian employee in the General Services Administration in post-World War II Germany, she returned to the United States and was hired by the newly formed Argonne National Laboratory. While there she worked on an early computer, AVIDAC, two more Argonne computers, ORACLE and GEORGE, and the first commercially available machine, the UNIVAC, in the mid-1950s. "She wanted to push the frontiers of science, even if just by a little," her son Jay told the Tribune. "She understood that the work she was doing was all part of the dawning of a new age -- the age of computers."