It is called the USS Arizona memorial and is built on the water above the wreckage of the USS Arizona.
The wreckage is considered a US National Historic Landmark.
The next day, December 8th, 1941, the US declared war on Japan.
Three days later Japan's allies, Germany and Italy, declared war on the United States.
They decided to strike in order to prevent the United States from attacking them.
The Japanese thought that if they took out the war ships in Pearl Harbor, then the United States Navy would be crippled and would never attack.
The United States was now a major part of World War II.
The US Navy was able to recover from the attack on Pearl Harbor fairly quickly.
However, all of the US ships but three (the Arizona, the Utah, and the Oklahoma) were able to be recovered and were used later during the war.
The biggest US loss was the sinking of the USS Arizona.