BACKGROUND: In March 2020, the greater New York metropolitan area became an epicenter for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The initial evolution of case incidence has not been well characterized. METHODS: Northwell Health Laboratories tested 46,793 persons for SARS-CoV-2 from March 4 through April 10. The primary outcome measure was a positive reverse-transcription-polymerase-chain-reaction (RT-PCR) test for SARS-CoV-2. The secondary outcomes included patient age, sex, and race if stated; dates the specimen was obtained and the test result; clinical practice site sources; geo-location of patient residence; and hospitalization. RESULTS: From March 8 through April 10, a total of 26,735 of 46,793 persons (57.1%) tested positive for SARS-CoV-2. Males of each race were disproportionally more affected than females above age 25, with a progressive male predominance as age increased. Of the positive persons, 7,292 were hospitalized directly upon presentation; an additional 882 persons tested positive in an ambulatory setting before subsequent hospitalization, a median of 4.8 days later. Total hospitalization rate was thus 8,174 persons (30.6% of positive persons). There was a broad range (greater than 10-fold) in the cumulative number of positive cases across individual zip codes following documented first case incidents. Test positivity was greater for persons living in zip codes with lower annual household income. CONCLUSIONS: Our data reveal that SARS-CoV-2 incidence emerged rapidly and almost simultaneously across a broad demographic population in the region. These findings support the hypothesis that SARS-CoV-2 infection was widely distributed prior to virus testing availability.