Some women who were involved in the abolitionist movement became aware that women had their lives restricted in some ways that were not unlike the restrictions put on slaves. At the anti-slavery convention in London in 1840, women delegates were not allowed to speak and were relegated to the gallery.
Lucretia Mott and Elizabeth Cady Stanton got talking about the unfairness of this situation, and this gave them the idea for having a convention to discuss women's rights, though it did not actually take place until 1848, at Seneca Falls.
Elizabeth Cady Stanton and other female abolitionists saw some similarities between the unfairness which with slaves were treated, and the unfair situation many women found themselves in, married women not being able to own property for instance, or obtain a divorce from a husband even if he was cruel or brutal to her.