Junction of U.S. Route 59 and Interstate 10, Houston, Texas
Interstate 10 (I-10) is the major east–west Interstate Highway in the Southern United States. In the U.S. state of Texas, it runs east from Anthony, at the border with New Mexico, through El Paso, San Antonio and Houston to the border with Louisiana in Orange, Texas. At just under 879 miles (1,415 km), the stretch of Interstate 10 crossing Texas, maintained by the Texas Department of Transportation, is the longest continuous untolled freeway under a single authority in North America, a title formerly held by Ontario's Highway 401. Mile marker 880 (and the corresponding exit number) near Orange are the highest numbered mile marker and exit on the Interstate Highway System or, for that matter, on any freeway in North America.
Texas alone contains more than a third of the interstate's entire length. El Paso, near the Texas-New Mexico state line, is 785 miles (1,263 km) from the western terminus of I-10 in Santa Monica, California, making it closer to Los Angeles than it is to Orange, Texas, 857 miles (1,379 km) away. Likewise, Orange, on the Texas–Louisiana state line, is only 789 miles (1,270 km) from the eastern terminus of I-10 in Jacksonville, Florida.
Leaving San Antonio, I-10 again passes I-410 and Loop 1604. I-10 is known as the 90th Infantry Division Memorial Highway on this stretch east of San Antonio. I-10 and US 90 continue their concurrency until they diverge in Seguin. They continue from there on to Houston nearly paralleling each other with short stints of overlaps along the route.
In Houston, from the western suburb of Katy to downtown, I-10 is known as the Katy Freeway. This section was widened in 2008 to as many as 26 total lanes, counting the six lanes of the access road, which are not limited-access and therefore technically not part of the freeway itself, but are directly adjacent. Between the West Beltway and the West Loop, the minimum lane count is 22 total lanes. In this section, the width is 24 lanes at multiple locations and up to 26 lanes east of Gessner Road (12 main lanes, 8 lanes of access roads, and 6 mid-freeway HOT/HOV lanes). From the Fort Bend county line to I-610, there is a minimum of four main lanes in each direction. The maximum number of undivided lanes at any point on the freeway is nine (though this includes one exit-only lane), in the eastbound direction approaching Antoine Drive; in the world, this is one of the widest sections of undivided highway in a single direction.The widest right-of-way, 556 ft (169 m), occurs at the Katy Freeway's intersection with Bunker Hill; at that point, the expansion plans called for six main lanes plus two toll lanes in each direction along with 10 lanes on the feeder/frontage roads. The actual striping after construction delineates 29 lanes including all 26 of the planned lanes plus an additional lane in each direction to enter or exit the toll lanes and one more turn lane on the eastbound feeder road.
Between I-610 and I-45 west of downtown, the Interstate contains at least five main lanes in each direction. Before 2008, this section had traditionally been the widest section of I-10 in the Houston area and the only one with a significant portion below grade. Starting in 2010, a project was started to widen the freeway, adding one extra main lane in each direction between Shepherd Drive and Taylor Street. In addition, the eastbound feeder road which ends at Studemont is being extended to Taylor Street. As I-10 travels through downtown, it junctions with I-45 and US 59, the future corridor of I-69 through Texas. Both interchanges feature left exits causing several lane shifts for through traffic. I-10 provides access to Minute Maid Park, home of the Houston Astros, and also runs through the campus of the University of Houston–Downtown.
The section east of downtown Houston is officially known as the "East Freeway," although it is widely known by locals as the Baytown East Freeway, or colloquially shortened to the Beast, due to a marketing push by Baytown, one of the largest cities in the Greater Houston Area.
In Beaumont, it is designated Eastex Freeway between both splits with US 69. Eastex is not to be confused with the designation for US 59 (Future I-69) in Houston.