TWIN FALLS, Idaho (KLIX) Idahoans can celebrate Historic Preservation Month by touring the state's roads through historic photos. This May the Idaho Transportation Department is reminding people of the archive of historic photos from years past that shows the development of the Idaho highway system. The online archive is free and has more than 30,000 images of roads and byways being build through Idaho.  The database has a search engine that allows visitors to find specific projects like the construction of the Perrine Bridge. ITD has also provided a how to video: