The Lapham Papers are organized as Personal and Biographical Papers, Correspondence, and Writing and Research Files.
Lapham's correspondence was extensive and in great part relates to his civic and scientific activities and to the interchange of information with other scientists, among them Benjamin Silliman, Asa Gray, James Hall, Charles Whittlesey, Leo Lesquereux, Cleveland Abbe, Samuel Stone, and officials of the Smithsonian Institution. His scientific acquaintances are also documented in a carte-de-visite photograph album. There is correspondence about his leadership in the Milwaukee County Agricultural Society, Milwaukee Public Library Association, Wisconsin State Agricultural Society, American Association for the Advancement of Science, Wisconsin Natural History Association, and the University of Wisconsin. Lapham also had frequent exchanges with Lyman C. Draper of the Wisconsin Historical Society.
The alphabetically-arranged research and writing subject files include draft and published papers, reports, and books, as well as data about archaeology, botany, cartography, geology, ichthyology, meteorology, paleontology, and the other areas of science in which he was interested. Additionally, there are notes on exploratory trips to various mineral regions, drawings of the Wisconsin effigy mounds, survey records for the proposed Milwaukee and Rock River Canal, and handwritten catalogues of plants and grasses, fish, fossils, minerals, and shells of Wisconsin and elsewhere. Records of Lapham's observations of weather conditions at Milwaukee for the Smithsonian and the U.S. Navy are detailed and extensive. There is also information on his role in the establishment of the U.S. Weather Bureau and on early weather forecasts made at Milwaukee. Related to this interest is data on water levels in Lake Michigan. Files on meteors, tornadoes, the drought and fires of 1871, the Wisconsin Geological Survey, and his concern over the loss of Wisconsin's forest trees further document the broad range of his scientific interests.
The photographs are a carte-de-visite album of 19th century scientists and a few portraits of Lapham and his family. They are part of the Personal and Biographical Papers section. Lapham's maps have been individually catalogued in the Wisconsin Historical Society map collection; his scientific library was donated by the Lapham heirs to the University of Wisconsin.
