Which state uses the postal abbreviation "AL"?

Whose presidential library is located in Boston, Massachusetts? Whose presidential library is located in West Branch, Iowa? Whose presidential library is located in Ann Arbor, Michigan? What is the two-letter postal abbreviation for Alabama? Montgomery is the capital of which state? In what year was Alabama admitted to the Union as a state? Which state is nicknamed the "Yellowhammer State"? What is the official nickname of Alabama?