We build a new, publicly available economic tracker that measures economic activity at a high-frequency, granular level. Using anonymized data from several large businesses – credit card processors, payroll firms, job posting aggregators, and financial services firms – we construct statistics on consumer spending, employment rates, incomes, business revenues, job postings, and other key indicators. We report these statistics in real-time using an automated pipeline that ingests data from these businesses and reports statistics publicly on the data visualization platform, typically with a lag of three days or less since the relevant transactions occur. We present fine disaggregations of the data, reporting each statistic by county and by industry and, where feasible, by initial (pre-crisis) income level and business size. We illustrate how the tracker can be used by measuring the economic impacts of the COVID-19 crisis on people, businesses, and communities and estimate the causal effects of recent local policy decisions. Going forward, we hope this tracker will serve as a public good that facilitates more precise targeting of policies and rapid diagnosis of the root causes of economic crises.