The four HoustonsI was thinking recently about how metro areas fragment as they grow. They stop being one unified city, and instead are an assembly of overlapping urban clusters where people tend to live and work within the same zone. Here's the main indicator: can most people reasonably commute to all or most of the jobs in the metro, or are there some areas that are essentially off-limits because of the extreme commute? Austin and San Antonio are still pretty much single cities. DFW is has grown beyond that point. You don't want to live in Frisco or Plano and work in Fort Worth. But where is Houston? Are we developing our own Ft. Worth equivalents?
I can see Houston fragmenting into four different clusters, based on both geography and industry.
The first, and main one, is roughly the triangle from Downtown to the Energy Corridor to Sugar Land. This is home to the vast majority of jobs, wealth, and amenities in Houston, including most of the dominant energy industry, as well as the world's largest medical center. West Houston has its own chamber of commerce.
The second one is not that far from the first, but distinctly different: the industrial east side along the ship channel, including Pasadena and Baytown, and home of the port, refining, and chemical industries.
The third one can trace itself back to the 60's, probably one of the earlier "edge cities" in America: Clear Lake and NASA. Well, that's the focus, but it's part of a larger coastal urban region that includes Galveston County, Friendswood, League City, Texas City, and Kemah (among others). NASA is probably the 'downtown/central business district' of this region, although Galveston might put up an argument there - almost their own little D-FW polarity. They also have their own chamber of commerce, Bay Area Houston.
You can probably guess where I'm headed with the fourth and last one: North Houston, focused on The Woodlands. I'd include Kingwood, Humble, IAH, Spring, Greenspoint, 1960, HP/Compaq, and Tomball in this zone. Originally this area was clearly a suburb of commuters headed into central Houston every day. It was the hot suburb when I moved there as a teenager in the early 80s. But I think The Woodlands has given it a new 'downtown', and increasingly people seem to both live and work out there rather than come into central Houston. Eventually I see this region focused on The Woodlands becoming our own Fort Worth, especially once the north side of the Grand Parkway gets built to unify the region with its own east-west freeway (well, in addition to 1960 and the north Beltway). The aerotropolis that evolves around IAH will also be a driver here.
Overall, I still think we're remarkably unified for such a large metro. As I mentioned here recently, we're the largest metro in the country that the census does not break up into multiple metropolitan divisions. Atlanta is the only other one in the top 11. But the growth, and at least some fragmentation, is inevitable. I'd love to hear your own perspectives in the comments.