People related to the history of transportation in Michigan. I spend a lot of research time on individuals, first, because people do things. It is a foible of railroad history (in particular) and business history more generally that people are taken out of the history and the company becomes the main actor - as in "the Michigan Central dug a tunnel" or "The Michigan Southern decided to build there." People make decisions and people do things, thus it is important to know who they are. Second, and related, is that to understand who our historical people were the researcher has to understand their social world. This includes who is in their family and where they lived. Does it matter that Frank J. Hecker and Charles Lang Freer were next-door neighbors? Does it matter that James A. McMillan and John S. Newberry were co-communicants at the Jefferson Avenue Presbyterian Church? What matters more than this is how their wives were related. Yes, it does matter that the Trowbridge, Hendrie, Sibley, Muir, and Russel families were all related to each other. All of these relationships shape the economic web of Detroit and Michigan. It is less important now, in the twenty-first century, because corporate ownership is so diffuse. But in the nineteenth century, social networks map rather neatly on to commercial and financial networks.