Access to child care centers reduces the care burden of parents, promotes child development, and creates employment opportunities. During the COVID-19 pandemic, however, many child care centers closed due to capacity restrictions and declining demand for in-person care. This study uses anonymized and aggregated mobile phone data to track year-over-year changes in visits to child care centers across most counties in the U.S. during each month of the COVID-19 pandemic. Our findings reveal that two-thirds of child care centers closed in April 2020, while one-third remained closed in April 2021. Moreover, we find that non-White families are more likely to be exposed to child care closures than White families. Our findings point to widening inequalities in access to child care and potential inequalities in the pace of labor market recovery after the pandemic subsides. We make our monthly-updated database on child care closures publicly available for use in future research.