The Texas Historical Marker Guide is a comprehensive app designed for iPhone users interested in exploring the vast history of Texas through its 16,000 historical markers. This app features an onboard database, allowing users to browse markers without needing an internet connection. Users can search for markers by geographic locations, governing agencies, and various topics. The app also provides information on attractions associated with the markers, such as museums and historic districts, enhancing the travel experience.

Additionally, the app utilizes Location Services to notify users when they enter different Texas counties, although continuous GPS use may affect battery life. Users can keep track of their visits to markers, update coordinates, and record conditions of the markers. The app also allows users to link marker records to photos from their library, share favorite markers through Mail and iMessage, and backup their data using iTunes File Sharing.