Houston, Texas map

Houston sits on the flat Gulf Coastal Plain about 50 miles inland from the Gulf of Mexico, connected to it by the Houston Ship Channel along Buffalo Bayou. Its location explains almost everything about its map: no hills, so the street grid runs unbroken for miles; bayous rather than rivers, so flooding shapes neighborhoods; and a port, so refineries and chemical plants line the east side.

The city extends into Fort Bend and Montgomery counties. The metro area, the largest in Texas, adds The Woodlands, Sugar Land, Pasadena, Katy, Pearland and Galveston.

Houston is the seat of Harris County, which counted 4,731,145 people in 2020 across 1,777 square miles — more land than the state of Rhode Island. Harris County touches Montgomery to the north, Liberty to the northeast, Chambers and Galveston to the southeast, Brazoria to the south, Fort Bend to the southwest and Waller to the northwest. Inside the county line, Pasadena (151,950 in 2020), Baytown, La Porte, Deer Park, Humble, Bellaire and West University Place are separate incorporated cities; the last two are enclaves surrounded on all sides by Houston.

There is no river through the middle of Houston. There are bayous: slow, flat-bottomed channels that drain the coastal prairie eastward into Galveston Bay. Buffalo Bayou runs west to east past downtown and becomes the Ship Channel below it; White Oak Bayou joins it at the north edge of downtown; Brays Bayou runs past the Medical Center; Greens, Halls, Sims and Cypress Creek drain the rest. The plain falls only a foot or two per mile toward the coast, so water moves slowly, and the heavy clay under most of the city absorbs very little of it.

That is the flooding problem in one sentence: a lot of rain, nowhere for it to go quickly. Two U.S. Army Corps of Engineers dams built in the 1940s, Addicks and Barker, hold back Buffalo Bayou west of Beltway 8; their reservoirs stay dry most of the year and are used as parkland until a storm fills them. Tropical Storm Allison in 2001 and Hurricane Harvey in August 2017 both flooded tens of thousands of buildings, many of them nowhere near a named channel.

The Houston Ship Channel is a dredged waterway about 50 miles long, running from the Turning Basin a few miles east of downtown, down Buffalo Bayou and across Galveston Bay to the Gulf. Congress funded the deepening after the 1900 Galveston hurricane and the channel opened in 1914, which is how a city 50 miles inland became a port. Port Houston moves more foreign waterborne tonnage than any other port in the United States, and the banks between the East End, Pasadena, Deer Park, La Porte and Baytown hold one of the world's largest concentrations of refineries and petrochemical plants.

The San Jacinto Battleground, where Texas independence was won in April 1836, sits on the channel near La Porte beneath a monument taller than the Washington Monument. A short way upstream the Lynchburg Ferry still crosses the channel free of charge, carrying cars where no bridge does.

South of Hermann Park and inside the 610 Loop, roughly between Fannin Street, Holcombe Boulevard and Brays Bayou, the Texas Medical Center is the largest medical complex in the world by employment and patient volume. MD Anderson Cancer Center, Texas Children's Hospital, Houston Methodist, Memorial Hermann, Baylor College of Medicine and UTHealth all stand inside a walkable district of a couple of square miles. METRORail's Red Line runs through it along Fannin and Main to downtown, and Rice University and the Museum District are immediately north.

Houston is the largest city in the United States with no zoning ordinance. Voters have rejected zoning three times, most recently in 1993, so land use is governed instead by private deed restrictions, minimum lot sizes, parking rules and platting standards. On the map that means the districts below are working names rather than legal boundaries, and a townhouse block, a warehouse and a taqueria can share the same street.