Wolf, in a statement, added nine counties to 10 already covered by the order, for a total of 19 counties and three-fourths of the state's 12.8 million residents.
The stay-at-home order starts at 8 p.m. Friday for Berks, Butler, Lackawanna, Lancaster, Luzerne, Pike, Wayne, Westmoreland and York counties, and will last until at least April 6.
The stay-at-home order restricts movement to certain health or safety-related travel, or travel to a job at an employer designated by Wolf's administration as "life-sustaining."
Wolf already issued such an order for the suburban Philadelphia counties, while the city has its own stay at home order in place.
The measures are designed to slow the spread of the virus and give the state's hospitals time to increase its staffing, equipment and bed space.
- Philadelphia reaches deal with Temple University for hospital space; 2 more COVID-19 deaths reported
There is no curfew, and no reports of police arrests for someone breaking the order. City officials under the order have generally said that enforcement is focused on letting people know about it, breaking up crowds or closing public areas to prevent people from gathering.
Wolf issued the first stay-at-home order Monday, a day after Philadelphia issued its own, and Health Secretary Rachel Levine said it's not clear yet whether the orders are effective.
"They haven't been in place long enough," Levine said at a news conference Friday. "It'll take weeks and weeks to see the effect."
Those new counties became candidates for the order as increases in confirmed coronavirus cases there grew to a "significant level and we have evidence of community spread," Levine said.
Even before Friday, Wolf had closed schools statewide, urged people statewide to stay home and ordered thousands of "non-life-sustaining" businesses to close, an order that has drawn lawsuits in federal and state courts.
Levine said those orders won't be relaxed until there is a consistent decline in the number of new cases that shows the measures are slowing the spread of the virus.
"We're not there yet," Levine said.
Meanwhile, Wolf signed a package of coronavirus-related legislation that passed the Legislature earlier this week.
A look at coronavirus-related developments in Pennsylvania:
Wolf's administration said on Friday it had confirmed more than 530 new cases, a 30% jump to more than 2,200, and six more deaths for a total of 22.
More counties, 50 of the state's 67 counties, are seeing their first coronavirus cases, while at least 17 nursing homes have reported a case, according to the state Department of Health.
Locally, the number of positive cases is currently:
Berks - 65
Bucks - 124
Chester - 107
Delaware - 185
Lehigh - 93
Montgomery - 374
Northampton - 79
Philadelphia - 637
More than 1,300 of Pennsylvania's confirmed coronavirus cases, or 60%, are in Philadelphia or its four suburban counties, and health care officials say they worry that hospitals there are two weeks away from being in the same situation as New York City's hospitals.
For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia, or death.
CONGRESSMAN TESTS POSITIVE
U.S. Rep. Mike Kelly of Butler County said Friday that he tested positive for the coronavirus.
In a statement, Kelly said he began experiencing flu-like symptoms and talked to his doctor, who ordered a test for COVID-19.
His test came back positive Friday afternoon. His symptoms are mild, he said. He was at home and was not in Washington for the vote on the $2.2 trillion economic rescue package.
Philadelphia Mayor Jim Kenney said Friday that the city has reached an agreement with Temple University to use the Liacouras Center and possibly other Temple facilities for overflow hospital space, including the pavilion and parking garage.
The Liacouras Center is a 10,000-seat multi-purpose center and will be able to handle at least 250 patients at first. City officials say they are moving quickly to get supplies and the physical aspects of the facility set up.
Meanwhile, a shuttered reform school for boys in suburban Philadelphia may be used as a medical overflow facility.
The Glen Mills School has medical and dental facilities, an air field, a generator and a more than 85,000 square-foot athletic facility that could host patients from hospitals and other health care facilities.
Tim Boyce, executive director of Delaware County's Emergency Management Agency, told WPVI-TV in Philadelphia that the Glen Mills School will start with 250 beds, but could be expanded.
Wolf's administration said Friday that the Pennsylvania Emergency Management Agency, along with federal and local government agencies, is assessing a number of sites across the state to become housing or medical facilities. No plans or agreements have been finalized, according to the administration.
As a whole, Pennsylvania has 37,000 hospital beds, although many are occupied.
Pennsylvanians filed another 48,000 unemployment compensation claims on Thursday, according to information from Wolf's administration.
That means Pennsylvanians have filed nearly 700,000 claims over the past 12 days as Wolf ordered thousands of "non-life-sustaining" businesses to shut down to help stop the spread of the coronavirus.
In the seven days through last Saturday, Pennsylvanians filed about 379,000 claims, the most in the nation and smashing the state's record for an entire week.
In the four days since then, Pennsylvanians have filed another 319,000, putting the state on course to break last week's record.