The women’s rights movement in the United States was first started by women who

The first gathering devoted to women's rights in the United States was held July 19–20, 1848, in Seneca Falls, New York. The principal organizers of the Seneca Falls Convention were Elizabeth Cady Stanton, a mother of four from upstate New York, and the Quaker abolitionist Lucretia Mott.

had experience in other social-reform movements

Explanation:

to finish the sentence, women who had experience in other social reform movements started the women's rights movement :)