March 7: First Missouri COVID-19 case reported in St. Louis County.
March 13: Missouri Gov. Mike Parson declares state of emergency in Missouri.
March 13: St. Louis County bans events with more than 250 people.
March 15: Jefferson County public schools announce closings.
March 16: Archdiocese suspends public Masses.
March 18: First COVID-19 death reported in state, and April’s municipal elections postponed.
March 18: St. Louis County bans events with more than 10 people.
March 20: First death in St. Louis County reported.
March 21: Parson announces social-distancing order, prohibiting public gatherings of more than 10 people. Both St. Louis and St. Louis County issue stay-at-home orders.
March 23: First COVID-19 cases reported in Jefferson County, and county Health Department and county government issue stay-at-home order.
March 27: Missouri National Guard mobilizes to help with COVID-19 testing.
March 27: Federal Coronavirus Aid, Relief and Economic Security (CARES) Act signed into law.
April 2: First COVID-19-related death reported in Jefferson County.
April 3: Parson announces stay-at-home order to begin April 6.
April 9: Parson announces school buildings will remain closed through the end of the school year.
April 23: St. Louis County exceeds 100 reported COVID-19 deaths.
May 4: State and Jefferson County stay-at-home order lifted.
May 18: Non-essential businesses may reopen in both St. Louis and St. Louis County.
May 18: St. Louis County Parks reopen.
June 15: Pools and gyms may reopen in St. Louis County.
July 2: First mask mandate in Missouri adopted in St. Louis and St. Louis County.
July 21: About 50 people gather outside the Jefferson County Health Department’s Hillsboro office to protest a possible mask mandate.
July 27: St. Louis County puts restrictions on bars and 25 percent capacity for businesses.
Aug. 24: Rockwood School District returns to school with all students online.
Aug. 27: The county Health Department Board of Trustees approves a face mask order but reverses the order less than 24 hours later.
Sept. 11-13: Eureka Days, which is held every September, is canceled.
Oct. 23: Youngest COVID death in Jefferson County announced, a woman in her 30s.
Nov. 1: An eighth-grade boy dies from COVID-19 in Missouri.
Nov. 13: Jefferson County Health Department reports 373 COVID-19 cases in a single day in Jefferson County, a record number.
Nov. 27: Jefferson County Health Department Board of Trustees passes face mask order in conjunction with county government.
Dec. 5: Missouri exceeds 5,000 reported deaths.
Dec. 14: Health Care workers and first responders start to be vaccinated.
Dec. 15: Mercy Hospital Jefferson in Crystal City receives shipment of Pfizer COVID-19 vaccines, the first in Jefferson County, and 10 staff members get shots.
Jan. 5: Missouri sets single-day record for COVID deaths: 263.
Jan. 14: Phase 1B Tier 1 vaccination plan activated.
Jan. 18: Phase 1B Tier 2 vaccination plan activated.
Feb. 3: St. Louis County holds first vaccine clinic.
Feb. 3: Jefferson County Health Department holds first vaccine clinic.
Feb. 7: First case of COVID-19 variant confirmed in Marion County.
Feb. 9: After spending 14 consecutive weeks at the highest level on the county Health Department’s COVID-19 warning system, the county is moved to second highest level, the orange status.
March 9: Jefferson County moves to the second lowest level on the COVID-19 warning system, the yellow status.
March 15: Phase 1B Tier 3 vaccination plan activated.