It seems as though he wasn't a particularly smart or kind man, and that most of his activities took place in Hispanola and the surrounding territories. So why is Christopher Columbus-ism so prominent in US schools and culture today (memorials, a federal holiday, an integral part of US history courses)?
A large part of the prominence accorded to Columbus comes from the assertion of Catholic identity. US society, particularly elite society, used to be relatively suspicious of Catholics, who were seen as not 'real' Americans in the way Protestants, even relatively recent Protestant immigrants, were. Catholics encouraged celebration of Christopher Columbus because he was a famous Catholic who had a crucial role in the founding of the USA*. It's not for nothing that the main Catholic fraternal order in the USA was called the Knights of Columbus. Although the Catholic/Protestant split has largely disappeared, the Catholics were so successful in encouraging celebration of Columbus' life and achievements that their accomplishment has outlived its original purpose and become another generic celebration of American identity.
*Not a direct role, I know, but I think it's safe to say that Columbus started the process that would eventually lead to the appearance of the USA.
Source: Ronald Takaki, 'A Different Mirror: A History of Multicultural America'