1869: "Every Woman Residing In This Territory May Cast Her Vote"

In 1869, Wyoming Territory assembled and elected legislature to draft laws for the territory which included a bill granting women in Wyoming full voting rights. The law passed, and women living in Wyoming Territory (and later state in 1880) cast ballots in their territorial and state elections. This groundbreaking legislation encouraged women suffragists across the United States to continue advocating for women's voting rights, eventually leading to the 19th Amendment to the U.S. Constitution in 1920. 

AN ACT TO GRANT TO THE WOMEN OF WYOMING TERRITORY THE RIGHT OF SUFFRAGE AND TO HOLD OFFICE

Be it enacted by the Council and House of Representatives of the Territory of Wyoming:

Section. 1. That every woman of the age of twenty-one years, residing in this territory, may, at every election to be holden under the laws thereof, cast her vote. And her rights to the elective franchise and to hold office shall be the same under the election laws of the territory, as those of electors.

Section. 2. This act shall take effect and be in force from and after its passage. 

This law will be in effect as soon as it is approved.
Approved, December 10th 1869.

Source:

An Act to Grant to the Women of Wyoming Territory the Right of Suffrage and to Hold Office, Library of Congress.