Public health infrastructure varies widely at the local, state, and national levels, and the COVID-19 response revealed just how critical local health authority can be. Public health officials created COVID policies, enforced behavioral and non-pharmaceutical interventions, and communicated with the public. This article explores the determinants of public health capacity, distinguishing between formal institutional capacity (i.e., budget, staff) and informal embedded capacity (i.e., community ties, insulation from political pressures). Using qualitative data and interviews with county health officers in California, this article shows that informal embedded capacity—while difficult to measure—is essential to public health capacity. It concludes by relating public health capacity to broader issues of state capacity and democracy.