Question: Which  international border is San Ysidro Port of Entry at  

Related documents: [0]  [DOC] The Mexico–United States border is an international border separating Mexico and the United States, extending from the Pacific Ocean to the west and Gulf of Mexico to the east. The border traverses a variety of terrains, ranging from major urban areas to uninhabitable deserts. s of 2010 , approximately 350 million legal crossings occur annually, and is the most frequently crossed border in the world. [END] 
[1]  [DOC] San Ysidro Transit Center is a San Diego Trolley station on the Blue Line and the southern terminus for this line. The previous station northwest is Beyer Boulevard. South of this station is the San Ysidro Port of Entry at the Mexico–United States border. The station serves primarily as a way to provide access to downtown for the thousands of international commuters and tourists who travel between San Diego County and Tijuana, Mexico. Its secondary purpose is to provide access to the large shopping areas, including the Las Americas Premium Outlets which are connected to the stop via a pedestrian walkway. An intercity bus station is located adjacent to the station. [END]  
Answer: The Mexico–United States border
The Mexico–United States border