How did Iowa become centre stage in U.S. politics?

The Iowa caucus play a central role in the U.S. presidential election cycle, but how did they come to be so prominent? Steffen Schmidt, or 'Dr. Politics' as he is known in Iowa, has been covering the Iowa caucus for over four decades. He is a political scientist at Iowa State University in Ames, and he explains how it turned out that all eyes are on Iowa.