It is located at the mouth of Tokyo Bay on Miura Peninsula. Developed amd used as a base by the Imperial Japanese Navy up to 1945, it now has bases of the United States Navy and the Maritime Self-Defense Force of Japan.
The Yokosuka Iron Foundry was established on the site of the city in 1865, and in 1866 the French engineer François Léons Verny came to Yokosuka and spent the next ten years supervising the development of shipbuilding facilities. The city itself was incorporated in 1907.
Koizumi Junichiro was born in Yokosuka.