Where in the Pacific Ocean did the U.S. test nuclear weapons in the 1940s and 1950s?

Bikini Atoll (meaning coconut place) is an atoll (an area with 23 islands totaling 3.4 square miles) in the Marshall Islands. This is the place where the United States tested nuclear weapons in the 1940s and 1950s.

Between 1946 and 1958, twenty three (23) nuclear devices were detonated by the United States at seven test sites located on the reef, inside the atoll, in the air, or underwater. They had a combined fission yield of 42.2 Mt (Milliton of TNT). Consequently, because of the testings, residents have not been able to return to their homes for almost 60 years.

Today, if visitors obtain prior approval, Bikini Atoll is open to those who are aboard vessels that are completely self sufficient; the vessels must not require any kind of external support. Also, the visitors must pay for a diver and two local government council representatives to accompany them. The local representation is required to verify that visitors don't remove artifacts from wrecks in the lagoon.