DENVER (KDVR) — Starbucks workers are lobbying to join a dwindling number of unionized workers in one of the nation’s least-unionized states.

Starbucks workers in Denver started striking on Friday morning to protest alleged unfair labor practices by the coffee chain. The Starbucks Workers United union announced the strike on Thursday. It started around 7 a.m. at the location at 2975 E. Colfax Ave.

Some workers have claimed that Starbucks has punished them in retaliation for supporting unionization, according to a press release.

Colorado’s union membership rates are at their lowest levels of the millennium.

Union membership numbers have been steadily falling since 2018. In 2021, there were 165,000 union members in Colorado — about 6.5% of Colorado’s workforce, down from 12% in 2018 and the lowest of the last 20 years.

Colorado lost union members at one of the fastest rates in the U.S. From 2020 to 2021, the percentage of the Colorado workforce that is unionized dropped 12.1%, the 17th-largest drop.

The state’s union membership rates have been historically lower than coastal states.

Colorado has the 19th-lowest rate of union membership in the U.S., sandwiched between Alabama and Iowa.

States with high union membership rates are clustered around the coasts and the Great Lakes. Hawaii has the highest rate, with 22.4% of its workers as union members. New York has the second-highest with 22.2%.

Interior and southern states have much lower membership rates. South and North Carolina have the lowest rates with 1.7% and 2.6%, respectively, followed by Utah, Texas and Arkansas with less than 4% apiece.