The United States Senate approved the naval base lease of Pearl Harbor in 1887 in the Reciprocity Agreement.
After discovering Hawaii, governments wanted to use it as a naval base. With this in mind, the United States presented an agreement for exclusive rights to Pearl Harbor in 1875. Without computers and the internet, the agreement took a while to work out between the Hawaiian King and the U.S. government. Finally, the Senate approved the agreement in 1887. Later that year the king also signed the agreement. Eventually, Hawaii joined the United States as the 50th state.