At Coronado National Park in Arizona, a human convoy walks unchallenged into the U.S. As amazing as it may seem, things are just as bad, if not worse, than before Sept. 11, according to a man who helps watch the park borders.
"It's going on every single night," says Dan Wirth, the Southwest border coordinator for the U.S. Interior Department.
The border patrol is responsible for all U.S. borders, but, as CBS News Correspondent Sharyl Attkisson reports, it is short-staffed. So, it's left up to the Park Service to police their own.
At a hearing Thursday, a Senate committee will examine evidence that U.S. homeland security is threatened by huge gaps in its front lines of defense, those same national parks straddling America's borders.
National parks account for 10 percent, or 100 miles, of the Canadian border and 37 percent, or 300 miles, of the Mexican border, and a scant 40 park service agents do the job. There are 30 agents along the Mexican border and 10 along Canada.
That makes tempting entry points for foreign criminals like the one who gunned down ranger Kris Eggles in Organ Pipe National Park in Arizona last August. Even the rangers themselves worry the parks are an open invitation for potential terrorists.
"There are indications that there are other people from other countries, including the Middle East, that are coming across our borders," says Wirth.
No one seems certain about who to blame for the giant security lapse. But some critics point the finger at the Interior Department itself, which oversees the national parks, saying it lacks focus, organization and training.
What's worse, some parks rangers complain they are ordered to look the other way.
"They are to let traffic flow freely from across the boundary, and they are not to enforce customs and immigration law," says Randall Kendrick, executive director of U.S. Park Rangers Lodge of Fraternal Order of Police.
Kendrick, who used to be a ranger himself, blames park superintendents with no law enforcement training and little understanding of what's at stake.
"I find that incredible," says Kendrick.
Now Congress is trying to figure out how to plug the holes. Until someone comes up with an answer, stealing into the U.S. even in these dangerous times is as easy as a walk in the park.