Grand Teton and Yellowstone National Parks have beautiful scenery and some intriguing history. Using old maps and public documents, the author has been researching the past and recording changes through time into the Open Historical Map. Old maps can be uploaded to the Mapwarper site, rectified and then used as image layers in JOSM. The images provide geometry and some date information. Early structures, highways and century-old changes in the Jackson Lake water level have been added to the OHM database. Using OHM’s time slider, changes through time can be easily visualized.