From the tragedy of hurricane Harvey to the elation of the Astros’ victory in the World Series, the Houston area had an eventful 2017. But some are remembering this year as much for what didn’t happen as for what did. They are remembering it as the year Harris County, which includes much of Houston, may have finally shed its nickname as the capital of capital punishment.

In recent decades, no county has been as prolific in its application of the death penalty as Harris County. If the county were a state, only one state would have executed more people since 1976, the year capital punishment was reinstated in the US: Texas itself.

But in 2017, for the first time in more than 40 years, no one from the county was executed. No one was sentenced to death this year either – in fact, no one has been sentenced to death since 2014. There is some disagreement over precisely why both numbers hit zero this year – and it could be years before it happens again – but experts see the landmark as a symbol of shifting attitudes toward the death penalty both in Harris County and around the country.

“We’ve been experiencing a generation-long decline in the use of the death penalty [nationwide], and the numbers in Harris County reflect that,” says Robert Dunham, executive director of the Death Penalty Information Center (DPIC), a national nonprofit organization that analyzes capital punishment statistics and issues.

There were 23 executions in the US this year, the second lowest total since 1991, according to the DPIC’s year-end report. (Only 2016 had fewer, with 20 executions.) The group projected a total of 39 new death sentences nationwide this year, the second-lowest in more than 40 years and the seventh consecutive year with fewer than 100 new death sentences nationwide.

Gary Cameron/Reuters Lead counsel Christina Swarns (c.) for Texas death row inmate Duane Buck (not pictured) walks down the front steps of the Supreme Court in Washington on Oct. 5, 2016.

Harris County averaged 12 new death sentences a year between 1992 and 1998, but has sent only 40 people to death row since 2000, an average of about two new death sentences a year.

There is no single reason why executions and death sentences have become so rare in the county, experts say, but there are several significant ones. Perhaps none is more significant than the change in Harris County district attorney.

From 1979 to 2000 the county had one D.A., a man named Johnny Holmes. His office sentenced more than 200 people to death – a record he believed meant he was doing his job. “This is what [prosecutors] are supposed to be – zealous in seeking justice,” he told the Houston Chronicle in 2007.

His recent successors have been more selective with when they pursue capital punishment against defendants, however.

Devon Anderson, the district attorney from 2013 to 2016, said the death penalty is only appropriate “for the worst of the worst.” Last year both she and her opponent, Kim Ogg, campaigned on platforms that included a more judicious pursuit of death sentences.

Ms. Ogg, one of several reform-minded prosecutors elected as local DAs in recent years, sought the death penalty in four cases this year. All four times, the jury instead sentenced the defendant to life without parole.

“The county is not the same place that it was when I was a prosecutor in the early ’90s,” she told Houston Public Media.

Indeed, another reason there have been fewer death sentences and executions in Harris County is because the general public has become less willing to deliver death sentences.

Twenty years ago, if prosecutors had the option to pursue the death penalty but opted not to, “you’d run the risk of paying for it in the next election because people would see you as being soft on crime,” says Jeff Newberry, a lawyer who represents Texas death row inmates and supervises students at the University of Houston Law Center.

Furthermore, “once you have an office that seeks death a certain number of times, it becomes easier for them to do it over and over again,” he says, because prosecutors become more experienced working capital cases and more adept at winning them.

Death sentences started to become a tougher sell to juries in 2005, however, when Harris County introduced the option of a life without parole sentence. Only 27 percent of people in the Houston area think death, not life imprisonment, should be the penalty for first-degree murder, according to a poll last year from the Kinder Institute at Rice University. Nationwide, the DPIC year-end report found that public support for the death penalty is at its lowest point since 1972, the year the US Supreme Court found death penalty laws to be unconstitutional.

The high court reversed that decision four years later. But in 2017 it issued two decisions in cases out of Harris County that are likely to further curtail the use of capital punishment in America.

In the case of Duane Buck, the Supreme Court overturned a death sentence that had been delivered with the help of racially biased testimony. And in the case of Bobby James Moore, the court ruled that Texas used outdated standards for determining whether or not a defendant is too intellectually disabled to be executed.

Both decisions addressed “some of the most unfair death penalty practices in the country,” says Mr. Dunham.

Still, both he and Mr. Newberry will be surprised if there’s a death-penalty hiatus in Harris County again in 2018.

“I don’t think there’s going to be no new sentences or executions next year,” says Newberry, “but I don’t think it’s going back to the levels we had 15 years ago.”