Annenberg Foundation
Annenberg Learner: A Biography of America: The u.s. Rail Network Around 1880
Annenberg Learner's series on Industrial Supremacy in America includes this map showing the major rail lines east of the Mississippi River in about 1880.
US Geological Survey
Usgs: Edna Derived Watersheds for Major Named Rivers
A watershed index where students can click on a map of the U.S. to find the names and locations of watersheds. Students can also download a file that can be run in Google Earth to view more about the watershed.