The rankings of the top 20 metro areas in the US over the past 200 years (click to enlarge):
Starting in the early 19th century, New York City has been number one and never given up that pole position. (It’s the Kentucky hoops recruiting class of big city populations.) Philadelphia, too, has been relatively consistent population-wise over the centuries — starting at number one in 1790 and standing at number five in 2010. Los Angeles, which only entered the top 20 metros in 1910, is now the second largest. Chicago — President Obama’s hometown — has risen from the mid-teens in late 1800s all the way to number three in 2010. …
Even more intriguing are the metros that have tumbled significantly over the decades.
Follow Detroit’s rise and fall and you follow the rise and fall of the manufacturing industry in America. The Motor City broke into the top 20 in 1840 and within 100 years was one of the five largest metro areas in the country. The last three decades have seen a population free fall in Detroit, however, all the way to the number 12 in 2010. St. Louis is now barely on the list after peaking at the fourth most populous metro area in the late 1800s. Baltimore has fallen from top five to barely top twenty.
He also looks at how current trends could change the electoral map:
In short, the demographic changes that began in the 1980s — population losses in the Northeast and Midwest, population gains in the South, Southwest and Plains — will only accelerate over the next few decades. … Republicans are right then to note that the states that will grow population-wise over the next five decades are in places where they have traditionally done well at the presidential level. But, the areas of growth within those states tend to be in places and groups where Republicans have struggled in recent elections. And, even if the 2060 map were in place in 2012, Romney still loses the election by a wide margin.