Sufjan Stevens' calling card has got to be his "50 albums for 50 states project." He's publicized his intention to write an album about each of the 50 states in the United States.
While this may sound a bit gimmicky, the project has attracted a lot of buzz and attention. Most people probably think it sounds a little bit crazy, and indeed it is. Sufjan isn't exactly a youngster, so that's a lot of albums for the rest of his lifetime. Most likely, Sufjan's stated intentions are a little disingenuous. Either way, Sufjan's decision to write albums that look at the American experience through the lens of individual states has allowed him to create interesting music about subject matter that not many artists would tackle (this song being a prime example).
This has also allowed Sufjan to showcase his abilities as a storyteller. Stevens has explained that the 50 states plan has acted as "a means of inspiration, by allowing me to focus on a particular subject. It's sort of like creating obstructions, giving myself certain terms within which to work." (Source)
This approach has certainly been effective, allowing Sufjan to write songs that combine historical facts with other more personal elements.