Guardian of the Green Card

At a construction site near the memorial, a work crew was directed with orders shouted in Spanish over the noise of heavy machinery. On the crew was Ernesto Valdez, 36, a native of the Mexican state of Guerrero. He came to the country illegally but received amnesty in the mid-1980s. The immigration documents allowed him to be hired on a project on federal property; without documents, he would have been excluded.

But requirements for regular construction sites are more lax, he noted. Despite tougher immigration laws, the lure of dollars remains strong.

"People keep crossing," said Valdez, wearing stained jeans, a white hard hat and a green vest. "It's a big problem."

On that point, Mercer would agree. And she is determined to do her part to stop it.

"You can't have a country if you don't have borders," she said. "If we don't do something now, we might not have another chance."

A Naturalized American

Mercer moved to Tombstone in 1992 after a divorce from a soldier ended the migration from base to base -- Florida, North Carolina, New Mexico, Germany and Arizona -- so common to military life.

They'd met when he was stationed in Germany, where Mercer was born and raised in a small town near Cologne.

She might never have become a U.S. citizen had she not been kicked off a local planning and zoning committee in Arizona when it was discovered she was not. In 1999, almost a quarter-century after coming to the United States, she was naturalized.

She remembers being one of about 500 people naturalized that day.

"Two of us were from Germany, one was Russian, one was Japanese and two were from Korea," said Mercer, who speaks with only the slightest hint of a German accent and thinks and dreams in English. "The rest, about 480 of them, were from Mexico."