Hector Aguilar walks to a border crossing station in Tijuana, Mexico, Jan. 11, 2018. Hector Aguilar is a U.S. citizen who works in San Diego, California, but lives across the border in Tijuana, in North Mexico's Baja California state. Aguilar travels almost daily from one side of the closely watched border to the other, as naturally as most people walk from one side of the street to the opposite. A long and well-guarded fence with just three gateways divides the two cities, a market of 6.5 million people and an economy that generates 230 billion U.S. dollars a year, according to Mexico's Foreign Ministry. (Xinhua/Xu Rui)