Apple employees at a store in Oklahoma City have voted to unionize, making them the second of the company's roughly 270 US retail stores to do so.

The result, announced by the National Labor Relations Board on Friday night, suggests that an initial victory by a union at a store in Maryland in June was not an isolated development in an organizing campaign that began last year.

The labor board says that 56 employees voted in favor of the union. The workers will be represented by the Communications Workers of America, which has members at AT&T Mobility and The New York Times.

The secretary-treasurer of the union said in a statement that workers at the Penn Square store had faced an aggressive anti-union campaign.

The open, direct and collaborative relationship we have with our valued team members is the best way to provide an excellent experience for our customers, and for our teams.

Health care, stock grants, and paid family leave are some of the benefits that employees at the store said they received. The company recently raised the minimum starting wage at its stores to $22 an hour and said it had increased starting wages in the US by 45%.

Workers said a union would bring greater transparency to their store because of the decisions supervisors made about hiring, pay and job assignments.

During the first year of the Pandemic, employees who worked from home were given different tasks, with little explanation for the differences.

Some people were making posters at home while others were on the phone taking calls. There wasn't a clear picture of what the plan was.

Workers said they were confused about how to earn promotions.

Some people have been in their current roles for years trying to get promoted and are not really getting anywhere, but when they get feedback on an interview for a promotion what they get is very subjective goals.

Workers were sometimes told to work on their customer focus, but not given more concrete suggestions like "I want you to have a three week average of 80 percent customer satisfaction score."

Mr. Forsythe said the idea of unionizing came to him late last year, after employees began to protest management's plan to bring them back to the office. The protest ballooned into a broader campaign, known as #AppleToo, that sought to highlight a variety of workplace problems.

A petition for a union election was filed by a store in Atlanta.

As the company announced a raise and highlighted the benefits it offered, the Atlanta store withdrew its petition.

The Oklahoma City store formed an organizing committee and more employees were interested in joining a union. In September, the Oklahoma City workers filed their petition.

Employees said supervisors held round-table discussions and one-on-one conversations in which they emphasized the drawbacks of a union, including the dues that workers would have to pay. According to these employees, supervisors told them that having a union would make it harder to change workplace arrangements when they needed to.

Workers at the Oklahoma City store said their market leader, who oversees several locations, was in their store a lot during the campaign, even though they would usually see him only a few times a year.

The impact of the company's response was limited because many employees did their own research about how joining a union would affect them, according to Patrick Hart, an employee at the store.

Mr. Hart said that all of them are very educated. We know how to look into something.