"Dat man ober dar say dat womin needs to be helped into carriages, and lifted ober ditches, and to hab de best place everywhar. Nobody eber helps me into carriages, or ober mud-puddles, or gibs me any best place!" And raising herself to her full height, and her voice to a pitch like rolling thunder, she asked. 'And ain't I a woman? Look at me! Look at my arm! (and she bared her right arm to the shoulder, showing her tremendous muscular power). I have ploughed, and planted, and gathered into barns, and no man could head me! And ain't I a woman? I could work as much and eat as much as a man – when I could get it – and bear de lash as well! And ain't I a woman? I have borne thirteen chilern, and seen 'em mos' all sold off to slavery, and when I cried out with my mother's grief, none but Jesus heard me! And ain't I a woman?"
--Sojourner Truth, Women's Convention in Akron, Ohio, May 29, 1851
Probably somewhat embellished, but it's the most widely repeated version.