HOUSTON — In what union leaders called one of the largest organizing victories ever in Texas, a majority of nearly 5,000 Houston janitors have signed to become members of the Service Employees union and initiated a process to bargain their first contract.

The union recognition process was carried out outside the province of the National Labor Relations Board after the city’s major building cleaning contractors agreed to a “card check” procedure. Under card check, a union is recognized when a majority of employees sign authorization cards. The American Arbitration Association, an independent agency agreed to by the union and the employers, certified the card count.

Janitors in Houston are currently the lowest paid and have the least benefits of similar workers in any big city in the U.S. “We work hard, but we aren’t paid enough to support our families or provide health care for our children,” said Maria Luisa Berlanga, a Houston janitor and mother of a 3-year-old son.

The janitors, on average, receive only $5.30 an hour and no health care. Most, like Erica Sandoval, who cleans offices in prime office towers, work part-time. A school dentist recently informed Sandoval that her 7-year-old daughter has cavities in six teeth, and fillings will cost $750, she told The New York Times. Her weekly take home pay is $91.50.

The organizing campaign, which emphasized the struggle for higher wages and health care benefits comparable to those of workers in other cities, was kicked off last April.

At a jubilant victory rally Nov. 30, the union detailed some of the tactics that led to the victory. The cause of the workers, nearly all of whom are Latina immigrant women, was supported by a broad coalition of religious leaders, community activists, progressive political organizations, and immigrants’ rights groups under the banner of “Justice for Janitors.”

Houston Mayor Bill White, a Democrat, has supported the movement along with a number of other political leaders, including members of Congress and the City Council. Archbishop Joseph Fiorenza of the Houston-Galveston Roman Catholic Archdiocese has also been a strong and vocal supporter. Justice for Janitors held several well-attended and very visible rallies in Houston.

Since the proposed union had no office or local in Houston, SEIU Local 1 in Chicago “adopted” the Houston janitors’ campaign, according to Local 1 President Tom Balanoff.

Dozens of the local’s Spanish-speaking members came to Texas for weeks at a time to talk with local janitors at their homes and workplaces.

Texas and the South and Southwest have historically been hostile to efforts of workers to form unions, so the janitors’ victory “inspires hope for the countless workers throughout the region who want to improve their jobs and their communities,” said SEIU Executive Vice President Eliseo Medina.

“We have seen so many unions and union members beaten down to the point they say it will never happen. But it did happen,” Harris County AFL-CIO Secretary Treasurer Richard Shaw told the World. “We are all elated,” added Shaw. “We worked closely with SEIU in support of their drive.”

The key to the organizing victory was pressuring the employers to agree to the card check procedure. Several large public-employee pension funds were urged by the union to put pressure on building owners and janitorial companies to forego anti-union campaigns. The four cleaning contractors who ultimately signed with SEIU — ABM, OneSource, GCA, and Sanitors — provide janitorial service for large buildings around the country. In many other large cities, their workforces are already SEIU members.

During a 10-day strike of Houston janitors this summer, 80 buildings in nearly two dozen cities honored the picket lines, the union said. The turning point came when the Teamsters announced that they too would honor the picket lines.

The next step for the janitors will involve negotiating for pay raises and health care benefits. In a statement issued at the victory rally, the union said that by negotiating a single agreement with a majority of the city’s cleaning contractors, the Houston janitors can bargain for improvements while ensuring that the companies remain competitive with each other, ending “a ‘race to the bottom’ in which contractors remain competitive by paying janitors as little as possible, instead of competing on issues of quality, efficiency and innovation.”

Tim Wheeler contributed to this story.