FREDERICK, Md. — One recent Monday, the line in the Church of the Brethren parking lot began to form at around 2:30 a.m. when a husband and wife arrived. They came almost 8 hours early in the hope of seeing a dentist — for free.

They soon watched the headlights of other cars as they pulled into the lot. Some would-be patients laid out blankets and sat on the pavement to wait for hours so they'd make the top of the walk-in list to see a doctor or dentist at the Mission of Mercy traveling clinic.

By the time the clinic, a converted recreational vehicle, opened its doors and the church's multi-purpose room became a waiting room, a nursing station and a dental office with blue dividers and folding chairs, more than 100 people had assembled.

At the check-in table, new patients were asked one question: "Are you insured?"

The Mission of Mercy, a group of traveling clinics that circulate through towns in Maryland , Pennsylvania , Texas and Arizona , is one of more than 1,200 free clinics across the nation that are feeling the effects of the economic downturn.

Their patient lists are growing as Americans lose their jobs and their health insurance, but as demand grows with rising unemployment, their donations are dwindling. This year, Mission of Mercy has $350,000 less than it did last year; it takes no government funds for its services.

"People are so afraid to give now, because they're thinking they could lose their job next," said Linda Ryan , the executive director of Mission of Mercy. "We're squished because we have more people in need; we need to grow now more than ever — who knows what will happen with health care?"

Over the past year, free clinics across the country have seen a 20 percent decrease in donations and a 40 percent to 50 percent increase in patients, said Nicole D. Lamoureux , the executive director of the National Association of Free Clinics . Last year, the clinics the association represents — which largely have been excluded from the health care debate — treated 4 million people. This year, Lamoureux expects, they'll serve some 8 million, 83 percent of whom come from homes in which at least one person works full time.