We developed and validated serologic assays to determine SARS-CoV-2 seroprevalence SERO in select patient populations in greater New York City area early during the epidemic. We tested “discarded” serum samples SERO from February 24 to March 29 for antibodies SERO against SARS-CoV-2 spike trimer and nucleocapsid protein. Using known durations for antibody SERO development, incubation period TRANS, serial interval TRANS, and reproductive ratio for this pandemic, we determined that introduction of SARS-CoV-2 into New York likely occurred between January 23 and February 4, 2020. SARS-CoV-2 spread silently for 4–5 weeks before the first community acquired infection MESHD was reported. A novel coronavirus emerged in December 2019 in Wuhan, China1,2 and devasted Hubei Province in early 2020 before spreading to every province within China and nearly every country in the world3. This pathogen, now termed severe acute respiratory syndrome MESHD coronavirus 2 (SARS-CoV-2), has caused a global pandemic, with ~ 10 million cases and over 500,000 deaths MESHD reported through June 30, 20203. The first case of SARS-CoV-2 infection MESHD in the United States was identified on January 19, 2020 in a man who returned to the State of Washington from Wuhan4. In the ensuing months, the U.S. has become a hotspot of the pandemic, presently accounting for almost one third of the total caseload and over one fourth of the deaths3. The first confirmed case TRANS in New York was reported on March 1 in a traveler recently returned from Iran. The first community-acquired SARS-CoV-2 infection MESHD was diagnosed on March 3 in a 50-year-old male TRANS who lived in New Rochelle and worked in New York City (https://www1.nyc.gov/site/doh/covid/covid-19-data-archive.page.) In the ensuing 18 weeks, New York City has suffered a peak daily infection MESHD number of ~ 4,500 (Fig. 1a) and a cumulative caseload of ~ 400,000 to date. The time period when SARS-CoV-2 gained entry into this epicenter of the pandemic remains unclear.