Who was Christopher Columbus?

Each year, on or around October 12, we celebrate "Columbus Day." It's a day off of school and work for many people. But why do we take a day off for this man? You probably already know that Christopher Columbus is credited with discovering America. The vast majority of historical studies, through the beginning of the 21st Century, celebrated Columbus as a brave explorer that was a great leader of men. We all could thank Columbus for discovering the land of the free; the bringer of European civilization to the new continent, etc. Yet other historians, especially over the last 20 years, have concluded that Columbus was not such a great guy; and some claim Columbus is to blame for thousands if not millions of American Indian deaths, due to conquest and disease. So which view is correct? Is either one correct?