In the Battle of Buena Vista (or, in Mexico, la batalla de la Angostura), February 22-23, 1847, Santa Anna's army of some 18,000 troops clashed with Gen. Zachary Taylor's force of around 4,500 troops, mostly volunteers. The heavily outnumbered Americans fought the Mexicans to a standstill on February 23 (11 years to the day after Santa Anna entered Bexar during the 1836 Texas campaign), and their victory decided the war in Northern Mexico.
For any interested in the Battle of Buena Vista, Google Maps now has street-level photo coverage of Highway 57 through the west side of the battlefield. It was photographed at fairly close intervals, and allows you to pan 360 degrees and zoom in with pretty incredible resolution. This virtual tour won't get you up into the gullies and plateaus where the bulk of the action occurred, but it will give you a picture of the lay of the terrain, the "Narrows" held by Washington's artillery, and the mouths of the successive ravines.
Go to www.maps.google.com and type the search phrase "La Angostura Saltillo Coahuila Mexico" If you zoom in where you can see a locale labeled "Angostura," that's a short distance north of the Narrows. Then, use the arrows on the highway to navigate back and forth, and use the compass at the top right of the image to pan 360 degrees.
The same street-level feature is available in Google Earth.