Porous U.S.-Mexico Border Stretches Across Arizona

MONTEZUMA PASS, AZ - MAY 02: A marker and a torn barbed wire fence stand between the United States and Mexico on May 2, 2010 at Montezuma Pass, Arizona. Although the U.S. government has spent billions of dollars constructing border defenses in the last decade, critics say that Arizona's border with Mexico was left with left with less protection, compared with California and Texas. Proponents of Arizona's new immigration enforcement law say the federal government has not done enough to stem the flow of illegal immigration into the state from Mexico. (Photo by John Moore/Getty Images)