Yokohama, pronounced yoh kuh HAH muh (pop. 3,220,331), is a Japanese port and a major center of commerce and industry. Among the cities of Japan, only Tokyo has more people. Yokohama lies about 20 miles (32 kilometers) south of Tokyo, on the island of Honshu. Yokohama is the capital of Kanagawa Prefecture. A prefecture is a political unit in Japan. Yokohama covers 163 square miles (421 square kilometers) on the western shore of Tokyo Bay and on the slopes of the surrounding hills. Downtown Yokohama occupies a triangular plain. The plain is bordered by narrow streams on two sides and by the bay on the third side. Residential areas of the city lie among the hills. Yokohama has a number of gardens, libraries, parks, and theaters. Universities in the city include Kanagawa University, Kanto Gakuin University, Yokohama Municipal University, and Yokohama National University. The city faces such problems as air and water pollution and lack of space. Overcrowded harbor conditions led to the construction of a pier that opened in 1970. The pier has special loading and unloading machinery to speed the handling of cargo. Yokohama is Japan's largest port in terms of cargo value. Ships leaving the city carry many products manufactured in Tokyo and other nearby industrial regions. Rail lines link Yokohama with such other major cities as Kobe, Osaka, and Tokyo. Shipbuilding is a major industry in Yokohama. The city's factories also make such products as automobiles, chemicals, electrical equipment, iron and steel, and machinery. Until 1854, the area that is now Yokohama was little more than a seashore with a few houses. That year, Commodore Matthew C. Perry of the U.S. Navy signed an agreement with the Japanese opening Japan to trade with the United States. Traders from a number of countries established offices in Yokohama in 1859. In time, Yokohama became a major seaport. The city has twice been almost destroyed. On Sept. 1, 1923, one of the worst earthquakes in history killed over 23,000 Yokohamans. In 1945, during World War II, U.S. bombers dropped thousands of fire bombs on Yokohama. The city later was rebuilt a second time. In 1973, a Yokohama law took effect that regulates new construction. It requires that no structure be built that allows sunlight to fall on the surrounding neighborhood less than four hours a day.