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Construction will begin Monday on an unmanned border checkpoint at Big Bend, a national park in a remote corner of southwest Texas, even as the federal government has been adding agents to patrol other parts of the U.S.-Mexico boundary.

U.S. officials say the crossing, the first of its kind on the southern border, is a concession to trade and tourism in an isolated stretch of hard country where visitors now have to travel a long distance to legally get across the Rio Grande and enter the U.S.

U.S. Customs agents stationed miles away will remotely scan travelers' documents, allowing visitors to pass easily between Big Bend and the Mexican village of Boquillas del Carmen, which has fallen on hard times as beefed-up border security has cut down on U.S. visitors.

Under the plan, surveillance cameras will monitor crossers at the entry point, which will be part of a visitors' center on the U.S. side. Park staff would be available to answer questions, and Border Patrol agents in the area would be on call to intervene if someone tries to skirt the system.

"It's one of the best things that's happened down here in the last several years," said Doug Lant of Terlingua, Texas, a small community just outside the national park. He said he was looking forward to frequenting Boquillas again to reconnect with a friend who ran the burro concession across the river.

Critics fear the absence of border agents will open the door to criminals—from visitors with fake IDs to drug traffickers moving illicit cargo. "Crooks will find a hole in the defense and that's what an unmanned border point is," said Kent Lundgren, chairman of the National Association of Former Border Patrol Officers, a group that says its mission is to advocate for a safe and secure border.

The number of illegal immigrants apprehended by border agents in the sector that includes Big Bend and stretches all the way to Oklahoma has fallen in recent years from more than 12,000 in 2001 to about 5,300 last year. That was the lowest number of apprehensions in any sector of the Southern border, where almost 450,000 illegal crossers were intercepted in 2010, according to Border Patrol statistics.

The unmanned checkpoint is expected to open in the spring, although U.S. Customs and Border Protection officials say plans are subject to change. It comes at a time when Republican presidential candidates are stressing the need for tougher border barriers. Rep. Michele Bachmann recently pledged to complete a fence to block northbound undocumented immigrants if elected president. Rival Herman Cain suggested an electrified wall, though he later said this was a joke.

Click for more on this story from The Wall Street Journal