Unzipped: Serious urban density in 77081

Despite the fact that Houston is the nation's fourth-largest city, much of the area within the Beltway looks more like suburbia. According to the folks over at the mapping and spatial analysis organization ESRI, the population density within most of Houston's ZIP codes falls between 1,000 and 5,000 people per square mile. And that's the range ESRI uses to define a place as suburban.

But while the average population density in Harris County figures out at 2,553 per people, there are a few spots within Houston where you're likely to be much closer to your neighbor. The top example of this is Gulfton's 77081, where 16,473 people are packed in per mile. That's 185 times the national average.

One hundred eighty-five times.

And it's way more jam-packed than the runner-up for population density. According to ESRI, the second-most dense part of town is next door, in Sharpstown's 77036, where 10,399 people live in each mile. Sharpstown also happens to be the largest ZIP code in the city by pure population count, with about 75,000 residents. But its borders encompass about twice as much land as those of 77081, accounting for a huge difference in saturation.

In much of America, density is determined largely by the size of residents' yards and the space between houses. But in Gulfton, there aren't many houses to be had. Nationally, 61.6 percent of homes are detached single-family houses. Not in 77081. Here, only 5.9 percent of homes are single-family. That's less than one-tenth the national average and way below the city average of 45.1 percent, according to the Census.

Clustering people into multifamily dwellings is an easy way to cram more people (and Gulfton residents are largely families) into an area. And the apartment complexes in Gulfton hold way more people than those in other parts of town. Sure, Gulfton has a few duplexes (172 to be exact), but 58.4 percent of the area's homes are located in buildings with at least 20 apartments. That's a massive share, compared to the city average of 21.6 percent, and the national average of 8.7 percent.

Bookmark Gray Matters. It's an easy way to cram more people into an area.