Nurses at St. Mary’s Hospital in Madison voted Thursday for a union in the largest representation election in Wisconsin in at least a quarter century.

According to a vote tally from SEIU Wisconsin, 511 St. Mary’s nurses voted for the union while 63 voted no — an 89% majority in favor of unionizing. SEIU Wisconsin is part of the Service Employees International Union. The vote Thursday was conducted by the National Labor Relations Board.

A total of 754 nurses were eligible to vote, according to the union.

St. Mary’s, part of the St. Louis-based nonprofit chain SSM Health, had campaigned against unionization.

Union supporters said in interviews in the last month that concerns nurses had raised about procedures, staffing and compensation had not received an adequate response from SSM Health management.  

“The landslide election is part of a growing national trend of healthcare professionals — including nurses, doctors and others — organizing unions to have a strong voice in improving patient care, staffing and retention,” SEIU Wisconsin stated in a press release issued after the election.

“With our union, we now have a strong voice to negotiate a contract with the policies, staffing, and retention we need,” St. Mary’s labor and delivery nurse Emily Berceau said in the union press release.

In a statement distributed by Lisa Adams, communications manager in the SSM Health Wisconsin regional office, the organization acknowledged that management would have preferred to see the union lose, which it characterized as “an outcome that allowed for continued direct engagement with our nurses.”

“Regardless, we remain committed to continuing to collaborate with our entire team to maintain a compassionate, high-quality, healing environment where we all can do our best work in living out our Mission to provide exceptional care for our patients,” the statement said. “It’s been our Mission for more than 100 years and one we hope SEIU Wisconsin will continue to respect.”

In addition to the nurses whose votes were counted, the union and the hospital management disputed whether 82 charge nurses were eligible to vote. While SEIU contends charge nurses are part of the group to be covered by the union, the hospital argues that they are supervisors and therefore not eligible.

The NLRB election order said the charge nurses’ eligibility would be decided later. The ballots of 66 charge nurses who voted were set aside as challenged and not counted Thursday. In its post-election press release, the union called on SSM Health to drop its objection to union coverage for the charge nurses.