Background Opioid misuse is a large public health problem in the United States. Residents of rural areas and American Indian (AI) reservation/trust lands represent traditionally underserved populations with regard to substance‐use disorder therapy. Purpose Assess differences in the number of opioid agonist therapy (OAT) facilities and physicians with Drug Addiction Treatment Act (DATA) waivers for rural versus urban, and AI reservation/trust land versus non‐AI reservation/trust land areas in Washington State. Methods The unit of analysis was the ZIP code. The dependent variables were the number of OAT facilities and DATA‐waivered physicians in a region per 10,000 residents aged 18‐64 in a ZIP code. A region was defined as a ZIP code and its contiguous ZIP codes. The independent variables were binary measures of whether a ZIP code was classified as rural versus urban, or AI reservation/trust land versus non‐AI reservation/trust land. Zero‐inflated negative binomial regressions with robust standard errors were estimated. Results The number of OAT clinics in a region per 10,000 ZIP‐code residents was significantly lower in rural versus urban areas (P = .002). This did not differ significantly between AI reservation/trust land and non‐AI reservation/trust land areas (P = .79). DATA‐waivered physicians in a region per 10,000 ZIP‐code residents was not significantly different between rural and urban (P = .08), or AI reservation/trust land versus non‐AI reservation/trust land areas (P = .21). Conclusions It appears that the potential for Washington State residents of rural and AI reservation areas to receive OAT is similar to that of residents outside of those areas; however, difficulties in accessing therapy may remain, highlighting the importance of expanding health care insurance and providing support for DATA‐waivered physicians.