California's Governor Gavin Newsom on Thursday ordered all Californians to wear face masks in public in a bid to stem the spread of the coronavirus.
"Science shows that face coverings and masks work," Newsom said in a statement. "They are critical to keeping those who are around you safe, keeping businesses open and restarting our economy."
His order came following a decision last week by officials in Orange County, south of Los Angeles, to rescind an order requiring people to wear masks in public.
Three other counties -- Fresno, Riverside and San Bernardino -- had also walked backed on requirements to wear face coverings because of public pressure.
"Simply put, we are seeing too many people with faces uncovered ? putting at risk the real progress we have made in fighting the disease," Newsom said. "California's strategy to restart the economy and get people back to work will only be successful if people act safely and follow health recommendations."
Numerous studies worldwide have shown that wearing face coverings reduce the risk of spreading COVID-19.
However wearing a face mask in many parts of the United States has increasingly taken on a political dimension. For many on the right, wearing a mask is seen as bowing to government authority, while on the left it is seen as beneficial to limiting the spread of the virus.
Newsom in mid-March became the first governor in the United States to issue a stay-at-home order and subsequently left it up to counties and cities to decide on whether to maintain the order as well as requirements on face coverings and other restrictions.
The issue set off a firestorm of controversy in Orange County, once a bastion of Republican politics, where some residents and local officials challenged an order to wear face coverings while in public, at work or a business where social distancing is not possible.
The county's health officer, Dr Nichole Quick, resigned last week after coming under scathing criticism and having a poster depicting her with a Hitler mustache on her face and swastikas during a meeting of the county Board of Supervisors.
She was also given a security detail after receiving what officials deemed a death threat.
Under Newsom's statewide order issued on Thursday, Californians or visitors must wear face coverings inside any indoor public space, while using public transport, in a taxi or in a ride-sharing vehicle.
They must also wear them at work or while outdoors in public spaces.
Children two and under are exempt as are people with medical or mental health concerns or developmental disabilities that prevent them from wearing a face covering.
Workers prepare face masks for rideshare drivers impacted by the COVID-19 pandemic at a food drive organised by the Mobile Workers Alliance (MWA), outside the Uber Greenlight hub in Burbank, California, June 11, 2020.
A man wearing a mask walks by a store requiring shoppers wear masks during the coronavirus pandemic, on May 27, 2020, in Los Angeles, California.