"Here it is," says John Hood, riffling through a portfolio. The drawing he pulls out was done as a prototype; it is crude and a bit frayed. But its characters, captured in silhouette, are instantly recognizable.

There is a father, leading the way with a clear sense of urgency, bent at the waist. A mother, running behind him, despite the prim dress that hugs her knees. A little girl, holding her mother's hand, unable to keep pace, her feet barely touching the ground, her pigtails -- everyone knows the pigtails -- flowing behind.

In 1990, the image would be projected onto black vinyl, traced with a knife blade, glued onto yellow signs, topped with one word -- CAUTION -- and placed on the shoulders of freeways, mostly along Interstate 5 north of the Mexican border.

The sign served as a warning that drivers could encounter people racing across the interstate -- most of them trying to get from Mexico into the United States. It would become one of the most iconic and enduring images associated with the nation's war over illegal immigration. And it would leave John Hood, now 59 years old and preparing to retire, conflicted and ambivalent about his strange legacy.

"What does it mean," he asked the other day, after sifting through his work, "to live a meaningful life?"

Hood was always an artist, always an observer.

A Navajo, he grew up on a reservation in a corner of New Mexico where people lived 7,000 feet above sea level, amid junipers and cedars, mountain lions and coyotes. His parents were illiterate; his home had no electricity or running water, and he slept on a pile of sheepskins.

"My childhood," he said with a smile, "was fulfilled in every dimension."

Hood went to boarding school, but much of his education came at home. His grandmother showed him how to shear their sheep and spin the wool into yarn. His grandfather showed him how to pick medicinal herbs and how to gather bright pollen from the tips of cornstalks to use in traditional ceremonies.

Hood illustrated many pieces of his life, sometimes etching his drawings on the walls of his family's barn.

"I used to watch the animals too," he said. "A horse will be staring away from you, but he can see you with his ears; you can see his ears going back and forth. It sounds weird, but you can learn from that. You can learn to be aware. You can learn to see."

Before he finished high school, he enlisted in the Marines. It was 1968. Within a year, he was in Da Nang. His tour in Vietnam was terrifying and defining. He often volunteered to walk "point" on patrol, and carried C-4 plastic explosives to blow up booby traps. His platoon called him "Chief."

Being an infantryman came naturally to him, or as naturally as it can come. Some of the tricks he used to survive had roots back home -- the way, for instance, that he could often locate the enemy by studying the sunlight filtering through the jungle canopy. He was in, he estimates, at least 20 firefights. Many of his comrades didn't make it.

"I lost a lot of things there," he said. "Friends. Youth."

At the end of his tour, he was sent back to the United States and stationed at Camp Pendleton. He was sure the war had left him with no enduring wounds, but he was wrong. He began having nightmares that a man was chasing him, a man he was helpless against. He went AWOL and got caught. He started drinking. His marriage fell apart.

Through the G.I. Bill, he started taking classes in fine arts at San Diego State. He was a particularly fine graphic artist, with an eye for delicate detail, for the interface of light and shadow. Shortly before he married a second time, he was hired as a graphic artist at the state Department of Transportation.

His portfolio would soon start filling up with routine projects: the cover of the department's phone directory, photo manipulations showing what freeways would look like with new carpool lanes. Then, in the 1980s, pedestrians started getting killed on California interstates with alarming regularity.

The state declared two "danger zones" along I-5.