The study found that the number of women held in the nation’s 3,200 municipal and county jails for misdemeanor crimes or who are awaiting trial or sentencing had increased significantly — to about 110,000 in 2014 from fewer than 8,000 in 1970.

(Over all, the nation’s jail population increased to 745,000 in 2014 from 157,000 in 1970.)

Much of the increase in the number of jailed women occurred in counties with fewer than 250,000 people, according to the study, places where just 1,700 women had been incarcerated in 1970. By 2014, however, that number had surged to 51,600, the report said.

And even as crime rates declined nationally, the trend toward jailing women in rural counties continued: Incarceration rates for women in sparsely populated counties rose to 140 per 100,000 in 2014 from 79 per 100,000 in 2000, the study found. During the same period, incarceration rates for women in the nation’s largest counties decreased to 71 per 100,000 from 76 per 100,000.

“Once a rarity, women are now held in jails in nearly every county — a stark contrast to 1970, when almost three-quarters of counties held not a single woman in jail,” the report said.

The counties with the highest rates of jailed women are nearly all rural and include Nevada County, Calif.; Floyd County, Ga.; and St. Charles Parish, La. Each has a population of fewer than 100,000 people but a rate of incarceration for women of more than 280 per 100,000, according to the Vera Institute.