Time is erasing hundreds of giant artworks from Chicago buildings, used as canvas during the 1960s and '70s, when muralists transformed gray city landscapes with color and dreams.

To Bill Walker, a public-art pioneer whose murals celebrate heroes of the civil rights movement, the decay goes deeper than the layers of paint on brick and concrete."We've lost something very important. We've lost compassion, caring and concern for all - much of that was expressed in the murals," he said.

Walker's powerful "Wall of Peace and Salvation, Wall of Understanding" is one of about 200 urban murals splashed across Chicago. A small movement is under way to save or restore some of the works, but there is little money to support it.

The mural was painted by the elevated tracks in the shadow of Cabrini-Green, a public housing project plagued by gang warfare, crime and violence. He chose the site, he said, because the mural concerns choices.

Commuters speed past its chipped and peeling images of Nobelist Martin Luther King Jr. and slain Black Muslim Malcolm X. A youthful Jesse Jackson is there as well. These heroes are contrasted with symbols of death and violence - the alternatives to a life of peace.

The fading images, 41/2 stories tall, still have a haunting presence, though much of their power is gone.

"I think the city is losing part of the civil rights struggle or human rights struggle," said Victor Sorell, an art history professor at Chicago State University. "Those murals are an index or a signpost of those times."

Their deterioration represents a loss of "neighborhood, city and community history," Sorell said.

Murals are an "outdoor museum," he said, especially in poor communities with fewer ways to preserve history and hope.

Chicago is considered the birthplace of the movement that produced these "blackboards for the people" and spread to other U.S. cities, especially on the East Coast and in the Southwest.

Walker's first outdoor mural, "The Wall of Respect" - created in 1967 with about a dozen other black artists from the South Side - is widely acknowledged as the first example of contemporary American community murals.

It was destroyed two years later, when fire gutted the South Side building that served as the canvas.

The Chicago Public Art Group uses city, state, federal and private funds to sponsor outdoor art work, but channels no money toward preservation, said muralist and group member John Weber, a professor of art at suburban Elmhurst College.

The city still funds new public art, preferring to spend resources on more permanent works than on restoring deteriorating murals.

Aurelio Diaz, who spearheaded the public art movement among Chicago's Hispanics, says the city should sponsor restoration of the murals that chronicle the issues and struggles of its people.

"It's not just art, it's a way of recording the history of the people," said Antonio Dos Santos, an artist who works with Diaz.

Luis Martinez, who owns an auto repair shop near a three-block-long Diaz work, said neighborhood residents and businesses "feel proud about these kind of murals. It's good for everybody and helps the community improve."

But Walker is resigned to the loss of his works. "The Wall of Peace" served a purpose in its time, he said, but perhaps that time is past. An artist by profession, he has touched up the lower sections of his masterpiece but never succeeded in restoring its original 1970 appearance.

"I'm sad I couldn't preserve it any longer, but I didn't have the financing," he said.

During the late '70s, Diaz and city-paid teenagers painted murals in the Pilsen neighborhood.

"The Legend of Bonampak," depicting an ancient Mayan fable, was executed with help from members of different neighborhood street gangs, recalled Diaz, 31, who emigrated from Mexico in 1971.

"The mural gave the kids a way to channel their creative energy," he said.

It covered years of graffiti and even now, after 11 years, there are only a few gang scrawls on the worn surface, Diaz said.

For years, Weber recalled, "the gangs wouldn't touch murals in other people's neighborhoods. One would not see graffiti on a mural."

Martinez, who stored supplies for Diaz and his teenage crew while they painted the "Galeria Del Barrio," still chops down weeds in front of the mural.

"Every week you can see some tourist buses stop to look at it," he said.