Very few, or at least relatively few, women have been executed in the United States. Kimberly McCarthy would have been the 13th woman put to death since reinstatement of capital punishment in 1976, had her execution not been delayed at the last minute to look into the question of improper jury selection at her trial. An African American woman, McCarthy was sentenced to die by a Dallas, TX jury that was predominantly (11-1) white.
So as it stand now, out of 1,321 executions in the U.S. only 12 (less than 1%) have been women. Interestingly, according to the Death Penalty Information Center, while women are responsible for roughly 10% of murders, they receive only 2.1% of death sentences and make up only 1.8% of current death row residents, but have received over 4% of clemencies granted. Perhaps this represents yet another way the death penalty is disproportionately applied.