Background Rates of sexually transmitted diseases (STDs) including chlamydia and gonorrhea are increasing in the United States while public health funding for STD services is decreasing. Individuals seek care in various locations including the emergency department (ED). The objective of this study is to investigate whether there are more physically proximal clinic-based STD care locations available to individuals who present to the ED in a major metropolitan area. Methods Addresses of EDs, clinics, and patients 13 years or older in St. Louis City or County given a nucleic acid amplification test and assigned an STD diagnosis (n = 6100) were geocoded. R was used to analyze clinics within 5 radii from the patients' home address and assess missed clinic opportunities (open, no charge, with walk-in availability) for those living in an urban versus suburban area. Results In urban areas, 99.1% of individuals lived closer to a clinic than the ED where they sought STD services; in suburban areas, 82.2% lived closer to a clinic than the ED where they presented. In the region, 50.6% lived closer to the health department-based STD care location than the hospital where they presented. Up to a third of ED patient visits for STD care could have occurred at a clinic that was closer to the patient's home address, open, no charge, and available for walk-in appointments. Conclusions Clinic availability is present for most of the individuals in our study. Clinics providing STD services can increase advertising efforts to increase public awareness of the services which they provide.