Objective (1) To examine usual source of care (USC) trends across four categories (No USC, Person USC, Person, in Facility USC, and Facility USC), and (2) to determine whether USC types are associated with emergency department (ED) visits and hospital admissions. Data Source 1996–2014 Medical Expenditure Panel Surveys. Study Design We stratified each USC category, by age, region, gender, poverty, insurance, race/ethnicity, and education and used regression to determine the characteristics associated with USC types, ED visits, and hospital admissions. Principal Findings Those with No USC and Facility USCs increased 10 and 18 percent, respectively, while those with Person USCs decreased by 43 percent. Compared to those in the lowest income bracket, those in the highest income bracket were less likely to have a Facility USC. Among those with low incomes, individuals with No USC, Person, in Facility, and Facility USCs were more likely to have ED visits than those with Person USCs. Conclusions A growing number are reporting facilities as their USCs or none at all. The impact of these trends is uncertain, although we found that some USC types are associated with ED visits and hospital admissions. Tracking USCs will be crucial to measuring progress toward enhanced care efficiency.