<P> The Brownsville & Matamoros International Bridge, a large swing bridge, dates back to 1910 and is still in use today by automobiles connecting Brownsville with Matamoros, Tamaulipas . It has not been opened since the early 1900s, though, when the last of the big steamboats disappeared . At one point, the bridge also had rail traffic . Railroad trains no longer use this bridge . A new rail bridge (West Rail International Crossing) connecting the U.S. and Mexico was built about 15 miles west of the Brownsville & Matamoros International Bridge . It was inaugurated in August 2015 . It moved all rail operations out of downtown Brownsville and Matamoros . The West Rail International Crossing is the first new international rail crossing between the U.S. and Mexico in 105 years . The Brownsville & Matamoros International Bridge is now operated by the Brownsville and Matamoros Bridge Company, a joint venture between the Mexican government and the Union Pacific Railroad . </P> <P> At the mouth of the Rio Grande, on the Mexican side, was the large commercial port of Bagdad . During the American Civil War, this was the only legitimate port of the Confederacy . European warships anchored offshore to maintain the port's neutrality, and managed to do so successfully throughout that conflict, despite occasional stare - downs with blockading ships from the US Navy . It was a shallow - draft river port, with several smaller vessels that hauled cargo to and from the deeper - draft cargo ships anchored off shore . These deeper - draft ships could not cross the shallow sandbar at the mouth of the river . The port's commerce was European military supplies, in exchange for bales of cotton . </P> <P> During the late - 1830s and early - 1840s, the river marked the disputed border between Mexico and the nascent Republic of Texas; Mexico marked the border at the Nueces River . The disagreement provided part of the rationale for the US invasion of Mexico in 1846, after Texas had been admitted as a new state . Since 1848, the Rio Grande has marked the boundary between Mexico and the United States from the twin cities of El Paso, Texas, and Ciudad Juárez, Chihuahua, to the Gulf of Mexico . As such, crossing the river was the escape route used by some Texan slaves to seek freedom . Mexico had liberal colonization policies and had abolished slavery in 1828 . </P> <P> In 1899, after a gradual change to the river position, a channel was dug for flood control which moved the river, creating what was called Cordova Island, which became the center of the Chamizal dispute . Resolving the dispute took many years and almost resulted in the assassination of the American and Mexican presidents . </P>

The part of mexico north of the rio grande used to be called