Data on people experiencing homelessness often come from time- and labour-intensive cross-sectional counts and surveys from selected samples. This study uses comprehensive administrative health data from emergency department (ED) visits to enumerate people experiencing homelessness and characterize demographic and geographic trends in the province of Ontario, Canada, from 2010 to 2017. People experiencing homelessness were identified by their postal code, designated as “XX.” Outcomes included the number of people experiencing homelessness stratified by year and week, gender and age plotted annually, the location of each ED visit, and composition changes in demographics and geographic distribution. Over seven years, 39,408 individuals were identified as experiencing homelessness. The number of ED visits increased over the study period in all of Ontario. The average peak in the number of visits occurred annually in September, with the fewest visits in January. Rises in overall homelessness were secondary to increases in working-age homelessness. ED presentations were concentrated in urban centres. The total proportion of patients experiencing homelessness became less concentrated in Toronto, decreasing from 60% to 40% over the study period, with a shift toward EDs outside the city. This study shows that administrative health data can provide comprehensive information on demographics and other characteristics analyzed over time. Surveillance can be conducted cost-effectively, and changes can be tracked in real time to allow for services to be coordinated and implemented in a time-sensitive manner.