One of the country’s oldest outdoor murals covers a storefront on Chicago’s Northwest Side. People who care about the 40-year-old painting are finishing a facelift. The mural restoration is doing more than brightening up a gritty stretch of North Avenue. It’s got Puerto Ricans in the Humboldt Park neighborhood talking about their heritage.

MITCHELL: A celebration of the restoration included music with roots in Puerto Rican slave plantations. José López of the Puerto Rican Cultural Center recalled the artists who painted the mural in 1971.

LOPEZ: Young Puerto Ricans from the street — people who were marginalized — decided to give us a legacy for our historical memory.

MITCHELL: The mural covers the side of 2423 W. North Ave. and includes portraits of nine Puerto Ricans who struggled for abolition and the island’s independence from Spain and, later, the United States. Three of them are on crosses. Those three all served long U.S. prison terms in the mid-20th century. The artists, led by Mario Galán, named the mural “La Crucifixión de Don Pedro Albizu Campos” after a Puerto Rican Nationalist Party founder. They put him on the biggest cross. López said the mural has special meaning in a part of Chicago where many Puerto Ricans can no longer afford to live.

LOPEZ: Gentrification means, many times, the writing away of people’s history.

MITCHELL: Restoring the mural took a decade. Neighborhood leader Eduardo Arocho attributes that to a developer who owned a vacant lot in front of the work.

AROCHO: His plans were to develop a three-story condo unit. We tried negotiating with him for several months, even at one point offering him several lots in exchange. And he refused and he just started to build the wall, covering the mural intentionally. And so that’s when we grabbed our picket signs and started to protest.

MITCHELL: The city finally won control of the lot and helped turn it into a small park to keep the mural visible.

PITMAN WEBER: It’s remarkable that this mural has survived.

MITCHELL: John Pitman Weber is a professor at Elmhurst College in DuPage County. He has studied and created public art for more than four decades. And he provided consulting for this mural’s restoration, carried out by Humboldt Park artist John Vergara.

PITMAN WEBER: Its content is unique, not only in Chicago but nationally.

MITCHELL: And aesthetics? Pitman Weber calls the mural formal and stark.

PITMAN WEBER: Kind of Byzantine, in a way, quasi-naïve — executed by some very, very young artists. The style possibly even adds clarity.

MITCHELL: Not all Puerto Ricans appreciate the artwork or the idea of the island breaking from the U.S. But when I ask the ones who walk by, most have strong attachments to the mural.

WOMAN 1: My mom used to go to St. Aloysius. My parents did and so…

MITCHELL: That’s a church right here.

WOMAN 1: It’s a church down the street. I used to go there when I was a little girl. And my mom would drive us to church and that’s how I knew we were getting close is when I’d see the mural almost every Sunday.

MAN 1: I see Don Pedro on the cross being crucified for what he believed in. Crucified the same way as Jesus!

WOMAN 2: I used to get up every morning and look at this mural.

MAN 2: I went to prison. I was 17 years old and I went to prison for 20 years. And, during those 20 years, when I used to think about home and I used to think about Humboldt Park, it was this mural that I used to think about.

MITCHELL: Why is that?

MAN 2: I remember when I was first looking at it, I think I was maybe 9 or 10 when I first noticed it, I didn’t know anything about Puerto Rican history. To me it was just a painting that was up there. I didn’t understand who was up there, what it was about. But when I went to prison I learned about my culture, I learned about who I was. I even got this guy on my arm. Two of these guys are on my arm.

MITCHELL: Tattoos.

MAN 2: Yeah, Pedro Albizu Campos on my right arm and I got Ramón Emeterio Betances on my left arm. And I think I can attribute that to this mural, man.

MITCHELL: The mural restoration will be complete with the addition of calligraphy this fall.