York also tweeted that San Diego was not a viable option despite overtures from its mayor's office.
After their games against Buffalo and Washington, the defending NFC champion 49ers will play at the Dallas Cowboys on Dec. 20 before returning to State Farm Stadium to play the Cardinals on Dec. 26. The 49ers are to host the Seattle Seahawks in a Jan. 3 regular-season finale.
The 49ers will play as many games at State Farm Stadium in December as the Cardinals (6-5). None of their games overlap on the schedule, and their Dec. 26 meeting will be broadcast via Amazon Prime Video, Twitch and, locally, on NBC Sports Bay Area.
Although State Farm Stadium hosted 4,200 fans in the Cardinals' past two games there, the general public is not allowed at the Cardinals' game Sunday against the Rams because of rising COVID-19 cases in Arizona; family members of Cardinals players and staff can attend, however. It's doubtful the 49ers will be afforded the same opportunity for Monday's game to mitigate cross-community exposure.
State Farm Stadium has a natural-grass surface and a retractable roof. The facility, located 20 miles northwest of downtown Phoenix, opened in 2006 and was formerly named University of Phoenix Stadium.
The 49ers were stunned to learn Saturday of the county's stricter guidelines, and Shanahan expressed "extreme disappointment" over that decision, which had the 49ers and their families scrambling for answers before and after Sunday's win.
"That's all we could talk about for the last 18 hours, because we got no answers from them," Shanahan said.
In response Monday, Santa Clara County Executive Dr. Jeff Smith said the county has been in regular contact with the 49ers "for months."
"It is hard for me to believe that the 49ers were surprised by the new orders given how serious the situation is both locally and across the country," Smith said. "They received a notice of the new orders as soon as the orders were finalized, at the same time we notified the thousands of businesses impacted in the community.
"It is impossible to notify anyone of the final decisions before they are made."