ObjectivesSixty-four state, local, and territorial health departments (HDs) in the United States (US) report monthly performance metrics on COVID-19 case investigation and contact tracing (CI/CT) activities. We describe national CI/CT efforts during October 25, 2020–December 24, 2021 which included three peaks in COVID-19 case reporting.MethodsStandardized CI/CT data elements submitted by the 64 HDs were summarized as monthly performance metrics for each HD and the nation. These included measures of CI/CT completeness, timeliness, and workloads. We calculated contact tracing efficacy as the proportion of new cases that occurred in persons identified as contacts within the 14 days prior to being reported as a case.ResultsA total of 44,309,796 COVID-19 cases were reported to HDs, of which 18,153,353 (41%) completed HD interviews. Less than half of interviews yielded ≥1 contact. A total of 19,939,376 contacts were identified; 11,632,613 were notified (58%), with 3,618,846 undergoing SARS-CoV-2 testing within 14 days of notification. Of the total reported cases, 2,559,383 occurred in recently identified contacts.ConclusionWe document the resource-intense nationwide effort by US HDs to mitigate the impact of COVID-19 through CI/CT before and after vaccines became widely available. These results document the coverage and performance of CI/CT despite case surges and fluctuating workforce and workloads.