In the summer of 2017 local, state and federal public health officials investigated an outbreak of E. coli O157:H7 infections in the Hildale/Colorado City community near the Utah and Arizona border. Twelve case-patients met the case definition. Eight were primary cases. Nine patients were hospitalized. Four patients developed Hemolytic Uremic Syndrome (HUS). Two patients died. Ten patients were under 5 years old. Investigators conducted a case-control study with 2 primary case patients and 16 controls. Sixty-seven percent of cases versus 19% of controls reported playing in an area that had manure (matched odds ratio; 95% CI, 0.8-71.3). Horse and cow manure samples collected from a case-patient's household yielded the outbreak strain. No common food or water source was identified. Contact tracing identified epidemiologic links between primary and secondary cases that supported person-to-person transmission.