Timeline of key events during the first 100 days.

Jan. 24:

A Santa Clara resident arrives from Wuhan, China. A week later, he would become the first person in the Bay Area to test positive for the new coronavirus. The county would declare a health emergency on Feb. 10.

Feb. 5:

Evacuees from Wuhan, where the outbreak began, land at Travis Air Force Base on a plane chartered by the U.S. State Department. They will stay at the base for a quarantine period.

Feb. 6:

The first known U.S. death from COVID-19 — a 57-year-old woman — occurs in Santa Clara County, though officials did not know it at the time. The death was announced in mid-April. It occurs three weeks before what was previously believed to be the first U.S. fatality, in Washington state on Feb. 28. The woman had not recently traveled abroad, so she is presumed to have been infected through community transmission, meaning an unknown source.

Feb. 16:

Evacuees from the Diamond Princess cruise ship, docked off Japan with hundreds of virus cases, arrive for quarantine at Travis Air Force Base in Fairfield. Others went to Lackland Air Force Base in Texas.

Feb. 25:

San Francisco Mayor London Breed declares a state of emergency due to the coronavirus. The city has no confirmed cases, but wants to ready resources for the virus’ arrival. City officials urge schools to draft plans for closures.

Feb. 26:

Health authorities report that Solano County has the nation’s first case of coronavirus from community transmission. (The earlier Santa Clara County cases were not yet known.)

March 4:

Gov. Gavin Newsom declares a state of emergency in California. The state has recorded 53 cases of the coronavirus and one death.

March 9:

The Grand Princess cruise ship docks in Oakland with infected passengers and crew. Hundreds of passengers head to Travis Air Force Base for a twoweek quarantine. Ultimately, more than 100 people who had been aboard the ship would test positive for the coronavirus.

March 11:

Newsom recommends postponing or canceling gatherings of more than 250 people. San Francisco bans gatherings of more than 1,000 people. Other counties around the Bay Area also enact restrictions, making for a patchwork of regulations.

March 15:

Newsom asks all Californians 65 and older, as well as those with chronic medical conditions, to isolate at home. He recommends that bars close and restaurants reduce capacity. He says the state will also limit visits in nursing homes and hospitals.

March 16:

Six Bay Area counties — San Francisco, Santa Clara, San Mateo, Marin, Contra Costa and Alameda — issue coordinated shelter-in-place orders that will take effect the next day. They permit only “essential” businesses to continue to operate on their physical premises. The remaining Bay Area counties soon follow. Across the state, 472

people have tested positive for the coronavirus and 11 have died.

March 19:

Newsom issues a shelter-in-place order for California, effective immediately. It is the most far-reaching order in the nation.

March 31:

San Francisco and other counties extend their shelter-in-place orders through May 3. State officials tell counties that schools will stay closed for the rest of the school year.

April 14:

Newsom lists six criteria he will use when deciding to ease state restrictions on schools, businesses and other gatherings. He gives no timeline and warns that even when restrictions are partially lifted things will be “anything but” normal, potentially until a vaccine arrives.

April 17:

Five Bay Area counties — San Francisco, Marin, Alameda, San Mateo and Contra Costa — unveil orders for residents to wear masks. The orders take effect April 18 and will be enforced starting April 22. Sonoma County issued a mask order several days earlier. Newsom says the state has suffered its deadliest day, with 95 deaths. April 27:

Six Bay Area counties — Alameda, Contra Costa, Marin, San Francisco, San Mateo and

Santa Clara — extend their shelter-in-place orders through May. Solano County had previously extended its order to May 17, and Napa County has an open-ended extension. Sonoma County also plans an update.

May 4:

Newsom says California’s economy can start reopening, with retailers in some counties able to reopen their businesses to curbside shoppers by the week’s end.

May 7:

Solano County says retailers, manufacturers, offices and some parks can reopen the following day. Along with Napa and Sonoma counties, Solano is moving faster than much of the Bay Area to reopen.

May 18:

San Francisco allows most stores to offer curbside service to shoppers.

May 28:

San Francisco officials unveil a plan to guide the city’s gradual reopening, including a timeline for schools, sports, gyms and restaurants. A new city rule also requires most people — including joggers — to wear a face covering outdoors when they are near others.

June 15:

Retailers in San Francisco begin allowing shoppers indoors, with restrictions. Offices in San Francisco are allowed to reopen to a subset of workers. But few people actually venture into stores or go to their offices.

June 17:

California reports more than 4,000 new coronavirus cases in a single day for the first time. The dismal record partly reflects increased testing capacity, but the accelerated reopening process is another likely factor. Health experts also expect new cases from weeks of racial justice protests.

June 18:

California issues an order requiring most people to wear masks outside of the home, effective immediately, if they cannot stay distant from others.