Chicago — On Chicago's West Side, if you board the L Train not far from the million-dollar apartments and pricey lattes of Lake Shore Drive in the downtown Loop, and then take a journey of just five city miles, you will notice that the housing thins out and the shopping fades. 

When you step off the train in the West Garfield Park neighborhood, you find residents' lives are, on average, 20 years shorter than they were in the Loop.

According to 2023 numbers from the Chicago Department of Public Health, in the Loop, the life expectancy was 87.3 years, the highest of any Chicago neighborhood. But in West Garfield Park, it was 66.6 years, the lowest.

That "death gap," as it is known in Chicago, is the largest for any big city in the U.S. Chicago residents have been aware of it for decades.

"Heart disease, cancer, homicide, overdoses, maternal infant health and accidents…add them up, you get a 20-year gap," Dr. David Ansell, senior vice president for community health equity at Rush University Medical Center, told CBS News. 

And in a live interview with "CBS Evening News" Wednesday, Chicago Mayor Brandon Johnson said that the life expectancy gap has been driven by homicides and drug overdoses. 

At New Mountain Pilgrim Missionary Baptist Church in West Garfield Park, Pastor Marshall Hatch says he has seen the gap remain wide for three decades.

He blames it in part on "isolation" and "segregation from resource." Crime, drug use and poverty all factor into cutting lives short, he says.

Johnson, who has served as mayor since 2023, argued that the gap has persisted for so long because local, state and federal leadership have "focused on neighborhoods like the Loop" and neglected neighborhoods like West Garfield Park. He called the gap a "real problem," adding that "we are working really hard, under my administration, to address it."

According to Hatch, few businesses, like grocery stores or fitness centers, have been able to thrive in West Garfield Park.

Hatch says there are "root causes" that have prevented Chicago city officials and police from addressing the crime and drug use in West Garfield Park and attracting financial investment to the area.

"I mean, ultimately, what you want to do, it's not about sweeping out people, but it's about redeeming people," Hatch said.  

For decades, Ansell says, redemption for West Garfield Park has been delayed by a lack of interest and investment, until now. His work with Rush Medical Center has led to the construction of a brand-new wellness center that will bring health care services and even a gym to this neighborhood, for what he hopes will be the start of a new cycle.

Hatch told CBS News that the wellness center is the first major community investment in West Garfield Park since the days of Martin Luther King Jr.

Ansell called that revelation "shocking."

"This was one of the greatest shopping districts in Chicago," Ansell said. "When he was assassinated, this neighborhood went up in flames and there was no reinvestment."

Johnson said that addressing the problem involves a combination of bringing in investment while lowering crime.

"The neighborhoods that deserve investment in education, healthcare and housing, we have to do that now," Johnson said. "But of course, we have to address these, you know, decades-old challenges that have been ignored for a very long time." 

Ultimately, Hatch believes the obstacles facing West Garfield Park are "absolutely" a government problem.

"We can't be a tale of two cities and be healthy and whole," Hatch said. "And I think that's what we find out in communities like this, where some of the violence spills out, none of us are safe unless all of us are safe. And I think that's what we find out in a grand urban experiment like Chicago."