Currently, Telsa's factory in Fremont, California is the only domestically located and owned assembly plant without union representation. Although the automaker has been previously regarded as a start up, CEO Elon Musk's decision earlier this month to boost production to 500,000 vehicles by 2018 would make the Telsa the 9th largest seller of new cars in the United States. This has prompted UAW President Dennis Williams to target the Californian plant; however, he claims the UAW will not be pursuing the plant in an "adversarial" fashion. The automaker ramped up production after its affordable Model 3 grew in popularity and plans to expand both Europe and China.
See "United Auto Workers eyes possible union push at Tesla factory", Gina Hall, Silicon Valley Business Journal, May 23, 2016