An open educational resource (OER) is a freely accessible resource such as a book with a creative commons copyright license. OER improves access to education by reducing costs. This may increase enrollment of cost-conscious students in introductory courses. Many science disciplines such as biology, chemistry, and physics already have several OER introductory textbooks available on Openstax.com, a leader in OER textbooks funded in part by the Bill and Melinda Gates Foundation. To address the absence of an OER geology text, faculty at Salt Lake Community College have written the first college-level OER textbook for introductory geology courses in the United States. The text is online at Opengeology.org/Intro, has interactive quizzes, videos and animations, and cited sources. The site is fully accessible with alternative text for figures and captioned videos, and is mobile compatible. The text was written collaboratively by four primary authors using shared Google Drive docs in "Suggestion Mode". Google Docs were electronically "shared" with fifteen external reviewers and three internal reviewers including university faculty, state geological survey staff, and professional geologists from industry. Reviewing a shared document in "Suggestion Mode" allowed for quick editing and easy collaboration. All figures are open access and the text is copyrighted under a Creative Commons Attribution-ShareAlike 4.0 International License in which users are free to share and adapt for any purpose with credit given to authors. Financial support for the project came from college administration.