The American Musical Theatre has always been shaped and stretched by innovation. Musicals that follow the patterns of other groundbreaking musicals may improve upon what the initial groundbreaker has done, but it's the musical that takes the first step outside of the box and convinces future creators to follow suit, that has generated the real growth within the art form. A handful of musicals have had the brazen audacity to do so. Today's column is a celebration of these movers and shakers of the musical form that have evolved the musical to where it is today. Not every title on this list is perfect, but each one changed what musicals could do and opened the doors for important new pieces to build on the foundations that they laid.