The 19th Amendment to the Constitution was first introduced in 1878. It took 42 years to become law in the United States (today is its 95th anniversary).
The text says: "The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any state on account of sex. Congress shall have the power to enforce this article by appropriate legislation."
Apparently, it was controversial that women be allowed the right to vote. 42 years. Seriously?
Sometimes, things that are most obviously wrong take a really long time to change. Thankfully, people didn't give up the fight. Patience really is a virtue. : )