North Dakota has become the 35th US state to require face coverings be worn in public, as governors across the country grapple with a surge in coronavirus infections that threatens to swamp their healthcare systems.
North Dakota joined 38 other states this month in reporting record daily jumps in new cases, 17 others with record deaths and 25 others with a record number of COVID-19 patients in hospitals, according to a Reuters tally.
"Our situation has changed and we must change with it," North Dakota Governor Doug Burgum said on Friday.
He also ordered restaurants and bars to limit diners to 50 per cent of capacity and to close by 10pm.
New cases nationwide rose on Friday to more than 177,000, the fourth straight day a record high was set, according to a Reuters tally of figures from US public health agencies.
The surge is straining many state healthcare systems as the number of COVID-19 patients in US hospitals rose to a record high 68,141 on Friday.
The US Centers for Disease Control has recommended mask wearing and one widely cited model has estimated that a nationwide mask mandate could save 68,000 lives by next spring.
Still, the issue has become politicised, with several Republican governors refusing to require them, saying it is a matter of personal responsibility, not government mandate.
US President Donald Trump has rarely been seen wearing a mask, except when was stricken with the virus last month, while his Democratic successor, President-elect Joe Biden, has sported one at nearly every public appearance.
With Thanksgiving and other holidays on the horizon, several governors, including those in California, Oregon and Washington, urged residents to avoid venturing out of state.
Gathering with family and friends, some governors warned, could transmit the virus through "living room spread".
The governors of six states in the northeast, the region hit hardest in the early months of the pandemic, were set to hold an emergency meeting this weekend to co-ordinate responses.
Since the pandemic began, the virus has infected 10,759,565 people in the United States, killing 244,324 of them, according to a Reuters tally.