March 29, 2013 -- For women seeking abortions in North Dakota, there's only one place to go.

Soon, it could close its doors.

For more than a decade, women have driven for hundreds of miles, sometimes up to eight hours, to visit the Red River Women's Clinic in downtown Fargo -- the lone abortion provider in North Dakota since 2001 -- then getting back in their cars after the procedure to drive home.

"It happens all the time," said Tammi Kromenaker, the clinic's director, reading off directions for a woman who was soon to travel six hours and 17 minutes from the heart of North Dakota's booming oil country.

"They'll drive through a blizzard, they'll drive through a flood," Kromenaker told ABC News. "We've had women who've hit deer on the way here, who've had flat tires on the way here, and they'll come through hell or high water because they don't want to be pregnant."

If a new law goes into effect, the Red River Women's Clinic will likely close -- leaving one of the nation's largest swaths without an abortion provider. The area would include western North Dakota, eastern Montana and western South Dakota, according to the Guttmacher Institute, a pro-abortion-rights research group.

To the east and south, the closest abortion providers to Fargo are three and a half hours away in Minneapolis, Minn., and Sioux Falls, S.D. To the west, the closest is in Billings, Mont., about 600 miles and eight-and-a-half hours away.

Red River's closure would leave a stretch of more than 800 miles across the northern Great Plains without an abortion clinic.

On Tuesday, North Dakota enacted the nation's most restrictive ban on abortions, prohibiting them as soon as a fetal heartbeat is detected, as early as six weeks into a pregnancy. The state overtook Arkansas, which passed a 12-week ban earlier this month, as the nation's least abortion-friendly state, and it's one of four states -- including Mississippi, South Dakota, and Wyoming -- with only one abortion provider.

The new law won't take effect until Aug. 1, but Kromenaker said patients are worried.

"We've already had phone calls today," Kromenaker told ABC News on Tuesday, a few hours after Republican Gov. Jack Dalrymple signed the law. "Is my appointment next week still OK? Can I still come in next week?"

Women who had just undergone abortions as Dalrymple signed the law were incensed about it in the clinic's recovery room, Kromenaker said. Since Tuesday, prospective patients have told Red River they think abortion is already illegal.

While the questions have kept coming, Kromenaker said she's not worried about the new law.

"I feel very confident that a judge, in looking at both the North Dakota constitution and the U.S. Constitution, will see that the U.S. Supreme Court has repeatedly, and despite numerous attempts to challenge it, has said you cannot ban abortion prior to viability," Kromenaker said. "I feel very confident that we will remain open and be able to continue to offer services during what will prove to be lengthy litigation."

The Center for Reproductive Rights announced plans to challenge North Dakota's new law in court. The group successfully challenged Idaho's 20-week abortion ban, which a federal judge overturned earlier this month, citing the Roe v. Wade ruling that states cannot prohibit abortions before a fetus reaches "viability," the point at which it could survive outside a mother's womb, which typically happens between 24 and 28 weeks.

"Although the likelihood of this measure surviving a court challenge remains in question, this bill is nevertheless a legitimate attempt by a state legislature to discover the boundaries of Roe v. Wade," Dalrymple said upon signing H.B. 1456.

Asked about the legal point, some anti-abortion activists have said they believe the Roe decision was flawed and that a later case, Planned Parenthood v. Casey, opens the discussion of when abortions can be banned. Others point to a political groundswell, as 11 states have now enacted abortion bans since 2010.

"What we're seeing in North Dakota is reflective of the grassroots passion across the country to take another look at this issue," said Mallory Quigley, spokeswoman for the anti-abortion group Susan B. Anthony List. "Forty years ago, the court sent down the Roe v. Wade decision and assumed that was it, but this is not settled law."

The Red River Women's Clinic's performs 18 percent of its non-chemical abortions before a fetus reaches seven weeks, meaning about 80 percent of its abortions will be banned Aug. 1 unless a judge says otherwise. While the clinic will look into expanding its services to keep its doors open, Kromenaker said it will probably have to close if the law takes effect.

"I don't think it'll come to that," Kromenaker told ABC News.

As of Thursday, the clinic said it had received $10,000 in donations, which it will earmark to fight the ban in court. The clinic performs between 1,200 and 1,300 abortions per year, and Kromenaker said North Dakota's sparse population can only support one clinic.

If the ban takes effect, Kromenaker predicted women in the region will resort to unsafe, illegal abortions.

"I don't even want to think about what that would mean for women here. It's frightening to think about that," Kromenaker said. "The bottom line is women don't care [if abortions are legal]. They don't want to be pregnant."