After the Constitution was written in 1787 how many states had to ratify it?

According to Article VII, the Constitution was required to be ratified by 9 of the 13 states before it went into effect. (2/3 of the total of 13)

This process was completed on June 21, 1788 with the ratification by the state of New Hampshire. All 13 eventually ratified, the last two being North Carolina (1789) and Rhode Island (1790).