Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: 1 in 59 children have autism. While similar rates of autism are reported in rural and urban areas, rural families report greater difficulty in accessing resources. An overwhelming number of families experience waitlists for diagnostic and therapeutic services. Objective: To accurately identify gaps in access to autism care using GapMap: a mobile platform that connects families with local resources while continuously collecting up-to-date autism resource epidemiology information. Methods: Resources were extracted from various resource databases. Resources were deduplicated, validated, and allocated into seven categories based on keywords identified on the resource website. The average distance between individuals from a simulated autism population and the nearest autism resource in our database was calculated for each U.S. county. Resource load, an approximation of demand over supply for diagnostic resources, was calculated for each U.S. county. Results: There are approximately 28,000 U.S. resources validated on the GapMap database, each allocated into one or more of seven categories. States with the greatest distances to autism resources include Alaska, Nevada, Wyoming, Montana, and Arizona. Of the seven resource categories, diagnostic resources are the most underrepresented, comprising only 8.83% of all resources. Alarmingly, 83.86% of all U.S. counties lack any diagnostic resource. States with the highest diagnostic resource load include West Virginia, Kentucky, Maine, Mississippi, and New Mexico. Conclusions: Results from this study demonstrate the sparsity and uneven distribution of diagnostic resources in the U.S., which may contribute to the lengthy waitlists and travel distances often necessary to receive diagnosis in specific regions. More data is needed on autism diagnosis demand to better quantify resource needs across the U.S.