First, why focus the question on private universities? Of course, public universities matter to cities, and had the University of Michigan not decamped from Detroit to Ann Arbor in 1837, the region's entire history might well be different (better or worse is hard to say). But that move was part of a bigger pattern. As University of Kentucky historian of higher education John Thelin notes, most leading public universities were established in what were, at least at the time, rural areas. Cheaper land, the domination of state legislatures by rural interests, the initial agricultural focus of many such institutions, and anti-Catholic and anti-immigrant nativism all pushed public campuses out into the country. That left private (including Catholic) institutions positioned for a greater impact in urban areas.

In the United States, private universities occupy a disproportionate share of the very top tier in wealth and prestige -- places that operate in education, research and health care on a scale that could substantially affect the economy of a city as large as Detroit. Yes, Detroit has public Wayne State and a smattering of mostly small and often Catholic private colleges. But while Wayne State does important work, and even a fair amount of research, its operating budget is $576 million. In Pittsburgh, Carnegie-Mellon and the quasi-private University of Pittsburgh are about $3 billion combined, in a city less than half Detroit's size.

Wayne State University doesn't do for Detroit what Duke University does for Durham. (Wayne State University)

Private non-profit institutions enroll fewer than 15 percent of U.S. undergraduates, but they account for 27 of the 60 U.S. members of the Association of American Universities, the leading group of elite research institutions, whose members employ on average 11,400 people each. In 1950, about the time Detroit's population began falling, private institutions were 18 of the 32 AAU members.

Today, the top 20 universities in the latest U.S. News & World Report rankings are all private institutions, as are 15 of the 20 largest university endowments. That dominance is regretted by many, but it's no coincidence. Top private institutions are more varied in their missions, and more malleable and flexible to respond to new opportunities and change direction. The best of them are more entrepreneurial and less bureaucratic. Those and other reasons have simply made them, historically, more appealing places for very rich people to give enormous amounts of money (and unlike any public university I know of, at a certain price they'll even name the place after you).

Of course, Detroit isn't the only major American city without a prominent private research university (Portland, Minneapolis-St. Paul and San Diego are all vibrant -- though the last two have large public research institutions). But it is arguably the most surprising. Detroit was once America's fourth-largest city, and not lacking in rich philanthropists. More to the point, a century ago, it was the Silicon Valley of its day, bustling with engineering talent, entrepreneurs, and venture capital. Imagine visiting Detroit in 1920 then journeying to the farmland of Palo Alto, CA, and finally the tobacco warehouses of Durham, NC. Which place would you have bet on to become a global research and education powerhouse? Yet among those three, only Detroit failed to do so. Frederick Rudolph's still-landmark history of American higher education, The American College & University was published in 1962, when Detroit still had over 1.5 million people. The city's name does not appear in this book, nor in Thelin's 2004 successor volume A History of American Higher Education.