Universal adult franchise means all adults have the right to vote besides those who are disqualified because of the laws of their country. This is a legal right guaranteed to everyone by the 15th Amendment in the United States Constitution.
Universal adult franchise is also referred to as universal suffrage. Universal suffrage was first meant to refer only to male suffrage. Once women gained the right to vote all around the world, the term applied to all adults. In America, universal adult franchise grew in the 19th century. Property requirements were removed for voting. After the American Civil War when slaves were free, adult black males were allowed to vote.