(NewsNation) — Thousands of nurses are on strike in Minnesota. The nurses say they’re fed up with understaffing, long hours, not enough pay and unsafe working conditions. Now. they’re demanding changes.

Out of concern for patients, union spokesman Sam Fettig said the nurses are opting for a three-day strike rather than an open-ended walkout.

Beginning Monday, nearly 15,000 nurses joined by community members and political leaders took to the picket lines.

“This is not about wages. Yes, wages are part of it, but it’s 100% staffing. That’s the number one thing we are fighting for inside that building,” a striking nurse explained.

Still, reports suggest nurses are seeking pay raises of more than 30% over the course of three years, while hospitals have currently offered around 10-12%.

According to the Minnesota Nurses’ Association, this may be the largest “private-sector” nurses’ strike in American history.

“Corporate health care policies in our hospital have left nurses understaffed, overworked, while patients are overcharged, local hospitals and services are closed, and executives take home million-dollar paychecks,” MNA President Chris Rubesch said.

The strike has impacted at least 16 hospitals in Minnesota’s Twin Cities area and nearby towns. To deal with the strike, the affected hospitals have hired thousands of temporary workers and traveling nurses.

Researchers say the three-day nursing strike could have a devastating impact on the health care system in Minnesota. But, this isn’t just an issue in Minnesota. A nursing shortage is happening across the country, with polling showing that top concerns among nurses nationwide are workplace violence and staffing issues.

An analysis from McKinsey & Company found the U.S. could face a labor gap of up to 450,000 nurses by 2025. To correct this, the study says the country would need to more than double the number of new graduates entering and staying in the nursing field every year for the next three years straight.

Angela Becchetti, a member of the Minnesota Nurses Association, spoke to NewsNation from the picket line. While staffing and pay do need to be addressed, she said violence against nurses is another issue that often gets overlooked by hospitals.

“There’s been shooting on campuses, nurses are assaulted every day,” she said. “We want that better protection, we want metal detectors at the entrances … to know that we’ll feel safe if we’re injured on the job.”

A statement on the Twin Cities Hospitals group website on Sunday said hospitals have asked the nurses’ union to join in mediation to help reach a “fair and equitable agreement.”

“A trained mediator can help parties focus on the key elements needed to move forward together,” the statement said. “However, the nurses’ union has rejected all our requests for mediation.”

The hospitals affected by the strike are operated by Allina Health, M Health Fairview, Children’s Hospital, North Memorial and HealthPartners. In Duluth, it is Essentia and St. Luke’s.

While there was another potential strike by nurses in Wisconsin at UW Health, one of the state’s largest health systems, this was averted when nurses and the UW Hospital board reached an agreement.

The Associated Press contributed to this report.