Jacksonville, the site of early European settlements on the northeast Florida coast, is a fine enough place – excellent sun, great crab shacks, sand dollar-strewn beaches, and the classic Floridian melting pot of cultures and accents.

But for those who do something really bad here in Duval County, this otherwise hospitable place is likely to turn on them, quickly and efficiently.

Per capita, the people of Duval sentence more of their neighbors to death than any other place in America. The equivalent of 1 out of approximately every 14,000 people who live in this urban county of 850,000 people has been condemned to die by lethal injection.

While much of the United States has gradually backed off the ultimate sanction, Duval County jurors have sentenced 14 people to death in the past five years for a litany of crimes, and 60 since the US Supreme Court reinstated capital punishment in 1976.

Death penalty critics tend to focus on wild-eyed prosecutors, vengeful judges, and bumbling defense attorneys as the problem with a national death row that runs 3,000 people deep. But interviews in and around Jacksonville indicate that Duval’s propensity for punishment by death comes in big part from the will of the people. Such views of residents haven’t been shaken by some 148 death row exonerations in the US since 1973 – 25 in Florida alone – including five in the US so far in 2014.

“If they done it, they done it, and it’s time to go,” says Buck Gergely, a bait dealer, in a typical response.

In many ways, Duval County is an outlier, part of the approximately 2 percent of US counties that are responsible for sentencing 56 percent of the nation’s death row inmates. Nevertheless, the attitudes here offer a window into some of the arguments that shape the debate over the death penalty – a sanction that a majority of Americans still support. The capital punishment debate has continued to be a US flash point this year, in particular as the country saw several botched executions in which convicts appeared to suffer.

In the South, deep-running honor codes, even an eye-for-an-eye culture, along with a penchant for violence are certainly part of the equation, especially here in Duval County, experts argue. “The sense of using violence and mob rule and the death penalty was familiar in what we think of as the frontier, and I think that the frontier never went away in the South,” says William Ferris, senior associate director of the Center for the Study of the American South in Chapel Hill, N.C., and author of “The Storied South.” “Tall talk, colorful language, and violence never disappeared.”

Amy Wood, a cultural historian at Illinois State University in Normal, adds a moral dimension to the discussion.

“Why Southerners have retained a culture of vengeance within the criminal-justice system is based in part on the idea of the criminal paying a debt to society, but also [of us affirming] our own moral values by how severely we punish that criminal,” she says.

To be sure, America writ large is thinking twice about the death penalty. This year so far has seen the least number of executions since 1994, and other Southern states such as Virginia and North Carolina are backing off capital punishment.

Some states with large death rows, most notably California and Pennsylvania, are carrying out executions only rarely. And juries in other states that have turned to the death penalty more often, including Texas, Virginia, and Missouri, are sentencing fewer convicts to death.

“When it comes down to it, the fact that we can’t figure out the right drugs to [administer], in essence that we can’t tie the noose right, that’s what’s driving public opinion more than the big questions about guilt or innocence,” says Seth Kotch, a historian at the University of North Carolina at Chapel Hill who is writing a book about the death penalty in the South.

But if political elites or enlightened juries are marginalizing the death penalty in some places, it’s a different story in states like Florida and Alabama, where populism and democracy play a key role. Neither state requires a unanimous jury decision to impose death, and both allow judges in some cases to transform life-without-parole sentences to death sentences. Also, both states elect judges and prosecutors, and Florida even elects public defenders, which means counties like Duval usually have a small cadre of individuals who directly reflect the will of the people in how they handle capital sentencing.

Jacksonville has become a unique place where residents “want the state, in the name of the people, to come in and avenge particular crimes,” says Ms. Wood, who edited the chapter on violence in “The New Encyclopedia of Southern Culture.”

From rough-and-tumble fishing villages to the east to the startling poverty of its Westside, Jacksonville is a lively Southern jewel where you might spot a cowboy in a laundromat, fish-plant workers communing with pelicans, or a lumber mill on Beaver Street. Beneath its sun-bleached veneer, however, lies a vexing truth: The corner of the state with the greatest proclivity for vengeance is also its most violent.

Instead of asking why so many death convictions, most local folks say, the real question is, why is the violent crime rate so high? Indeed, Duval leads other Florida metropolitan areas such as Miami-Dade and Tampa in nearly every violence metric, from murder to rape, domestic violence to gun crimes. While other jurisdictions have seen declines in violent crime, Duval County’s rate hasn’t budged.

“There’s deviance here,” posits A.J. Johnson, outside his home in Mayport, a nearly 500-year-old fishing community that was the site of a mass murder in 2003.

County residents cite other factors as contributing to the high rate of death sentences: the influence of military culture from nearby Defense Department installations, elected prosecutors, and Jacksonville’s proximity to the Florida State Prison in Raiford, where death row inmates wait.

To many critics, today’s death penalty-prone corners are the continuation of a Southern system of justice by lynching, originally set up largely to punish blacks. At the very least, studies show a propensity by juries to punish black defendants more harshly in capital cases, especially if they killed a white person.

For many critics, the fact that death rows, including Florida’s, are disproportionately made up of black convicts affirms that propensity, although supporters argue that death row demographics are largely commensurate with broader violent crime statistics.

“In some of these counties where race plays a certain role, especially in white flight areas, there’s fear that crime is coming from poorer people or minorities. It’s a back-against-the-wall sort of feeling that we need to have the death penalty to maintain law and order,” says Richard Dieter, executive director of the nonpartisan Death Penalty Information Center in Washington.

Florida Assistant State Attorney Bernie de la Rionda is known for his courtroom prosecution of George Zimmerman, but he also has a 31-year record of prosecuting capital cases in the Fourth Judicial Circuit, which includes Duval County. Prosecutors in the county, he says, know that a large majority of residents don’t have a problem with the high capital conviction rate.

“We live in a conservative county ... that values personal responsibility, which means that people here also value personal accountability,” he says.

Donna Cargill is among those who support the death penalty wholeheartedly. “They need to kill them,” says the biker bar waitress, pointing to news of shootings and killings in the city’s impoverished and largely African-American Westside.

But Ms. Cargill later reveals that her son has twice been sent to Florida State Prison for committing crimes against children. (She claims he is innocent.) Until the US Supreme Court ruled otherwise, even Floridians who had not been convicted of killing someone could face death for particularly heinous cases of molestation.

Mr. Johnson says his estranged daughter, a gang member in Newport News, Va., has twice been accused, but not convicted, of murder. He hopes she will avoid a third time, especially in Duval County.

“The punishment should fit the crime, but it’s a fine line,” he muses.

Although he supports the death penalty in general, he says the courts put too much focus on the details of certain murders, and not enough on trying to understand why those crimes happened.

Mr. Kotch sees use of the death penalty as part of longstanding patterns.

“We know that the best predictor of execution is previous execution, which suggests that a courthouse or a county can get into a habit of doing things, and those habitual behaviors are informed by cultural cues about crime and punishment,” he says.

Still, support for the death penalty in a place like Duval presents a bit of a paradox, because such regions in the South tend to politically oppose centralized power. “The fact that the death penalty is the most profound way a government can intervene in the life of a citizen would seem to cut against sort of [antigovernment] politics in the South,” Kotch says. “Yet it somehow manages to line up.”

Yet things are changing somewhat.

While Texas still executes more people than any other state, the number of death row convictions has gone down, with fewer such convictions this year than executions – part of a five-year trend. The election of the first black district attorney in Dallas, some suggest, has led to a dwindling number of convictions there. And mostly because of demographic and procedural changes, Virginia and North Carolina have de facto moratoriums on executions.

Even Duval County has seen a slight dip in the number of death row convictions in the past few years.