I was looking at the Boston media guide today and saw the following. On BAA's list of top American women. They list 9 American women who have broken 2:20 at Boston including six under Radcliffe's world record.
http://www.bostonmarathonmediaguide.com/7-topfinishesamericanwomen.php
985 Lisa Larsen-Weidenbach Michigan 2:14:05 1
1984 Midde Hamrin Texas 2:33:53 2
1983 Joan Benoit Massachusetts 2:09:00 1
1982 Eileen G. Claugus California 2:38:48 3
1981 Patti Lyons Catalano Massachusetts 2:27:51 2
1980 Patti Lyons Massachusetts 2:35:08 2
1979 Joan Benoit Maine 2:09:27 1
1978 Gayle S. Barron Georgia 2:10:13 1
1977 Michiko (Miki) Gorman California 2:14:46 1
1976 Kim Merritt Wisconsin 2:20:19 1
1975 Kathrine Switzer New York 2:51:37 2
1974 Michiko (Miki) Gorman California 2:13:39 1
1973 Jacqueline A. Hansen California 2:16:03 1
1972 Nina Kuscsik New York 2:15:39 1