On the first Thursday of every month, with the exception of July, nearly 300 children without visas, as well as their families or guardians, cross the border from Mexico into Nogales, Ariz., with the cooperation of Customs and Border Protection, as a special permission to enter the U.S. for healthcare reasons.

PHOTO: Andrew Brown
Mr. Yepiz brings his twin sons to the clinic for care.

Then, they travel by bus and van 3 miles north of the border to St. Andrew's Children's Clinic. There, children with a variety of disabilities and those accompanying them gather in the dirt parking lot before being registered and processed for treatment. For some, it is their first visit, but others have been making this journey since birth.

“We really specify that the children we see are children from Mexico and living in Mexico and that they do not have other resources," said Dr. Francisco Valencia, a pediatric orthopedist from Tucson, and the medical director at St. Andrew’s Children’s Clinic.

“We’ve had people who literally travel over a thousand miles, we have people who come from the southern part of Mexico and easily take a two-day bus trip," he said. "You could imagine what a two-day bus trip is like for you and I, let alone traveling with a child who has a disability. Just trying to carry them onto the bus and trying to care of their needs, whether it’s feeding or changing their diapers or other necessities."

PHOTO: Andrew Brown
Dr. Francisco Valencia at St. Andrew's Children's Clinic

The nonprofit clinic has been providing free medical care to impoverished Mexican children for more than 40 years. It doesn't receive any government money, relying exclusively on grants and private donations. The annual operating budget of the clinic itself runs just over $400,000, with 98 percent of that applied directly to patient care. The nearly 50 members of the professional healthcare staff volunteer their time.

“Our clinic is a church, St. Andrew’s is a church, but there’s no proselytizing going on, I think the families recognize there is a spiritual component and it makes them feel better in what they are doing...the church is very gracious, they rent the facility to us for a dollar a day and they vacate the premises and we take over, we occupy every corner and every nook of this facility,” Valencia said.

The children who come to the clinic suffer from a wide variety of disabilities and medical conditions, including cleft palate, spina bifida, brittle bone disease, epilepsy, Down's syndrome, hearing loss, vision loss and speech impediments - some have no speech at all, and others were born without arms or legs.

PHOTO: Andrew Brown
16 year-old Lupita Montes-Guitterez having her prostheses adjusted by clinic volunteers.

Once a patient begins treatment, the clinic continues care until age 18. But while the healthcare is free, it’s not cheap.

Shriner’s Hospitals, based in Sacramento, Calif. and Spokane, Wash., provided nearly $3 million worth of pro bono patient surgeries for the children of St. Andrew’s in 2012. Also, Shriner’s Hospitals send at least one doctor and one nurse to each month’s clinic to provide diagnoses and care.

“There’s always negative news that come out of the border, we always hear about the violence, we always hear about the immigration issues and the...ugliness of the wall that goes up, but we never really hear the positive things that people do on the border, and this is one of those grassroots efforts that has really made a difference," Valencia said. "What we do and what I hope we continue to do is make people aware that in their own backyard, something good is happening."