Pearl Harbor is significant because it was a day that ultimately changed history by causing Americans to join together in the war effort.Before Pearl Harbor, the country was divided and not all Americans wanted to be a part of World War II. After Pearl Harbor, the support for the war became unanimous. The attack ensured America’s entrance into the war. Pearl Harbor made Americans passionate about the war and provoked a joint effort by all, at home and overseas.On that fateful morning, Dec. 7, 1941, everyone united. Civilian employees helped to load and clean weapons, wounded men fought on, doctors from miles away rushed to the scene and — when blood donations were needed — donors stood in line for almost seven hours to do their part.Only a few hours after the Japanese attack on Pearl Harbor, Japan formally declared war against the United States.The sentiment Americans felt is best explained by the words of fleet Chaplain William A. Macguire: “Don’t say we buried our dead with sorrow. They died manfully. They were buried manfully. And we will avenge their deaths, come what may.”Pearl Harbor infuriated Americans and motivated an undivided decision to enter into World War II. On Dec. 8, 1941, the United States joined the Allied Powers.The outcome of World War II may have been entirely different if the United States had not joined the Allied Powers. The United States implemented the draft and all men from age 18 to 45 were included, providing over 16 million troops. All automobile factories in the United States stopped production of cars and began manufacturing only vehicles and planes for the war. Women went to work in factories to make war supplies and some even joined the armed forces. Without the United States providing so many troops and supplies, the Allied Powers may not have won.Although the attack on Dec. 7, 1941, may not be our proudest day, there are many positive outcomes and effects too often overlooked. We can look back on this day and be proud that we live in a country where people forget themselves and do whatever it takes to help each other in a time of need and unite toward a common goal. Without our combined efforts, the outcome of World War II could have been entirely different, and we would be living in a different world. Pearl Harbor changed the course of history.