Lake Okeechobee, the largest lake in the United States south of the Great Lakes, is the hydrologic lynchpin of CERP. However, early accounts of this lake are inaccurate or nonexistent in historic documents such as the 1834 and 1861 Florida maps (3). The first European explorers to cross the Everglades did so in the mid- to late 19th century. Lt Col. William Harney entered "The River Grass" in 1840 near Fort Dallas (present day Miami) and exited on the southwest side via a tidal channel that still bears his name, the Harney River. Hugh Willoughby's expedition sailed up the Harney River and pushed their way across the southern Everglades to an area south of Miami in 1893. In 1882-3 the New Orleans Times-Democrat sponsored two expeditions that explored the Caloosahatchee River, Lake Okeechobee, and the sawgrass plains south of the Lake (Peoples and Davis 1950, 1951; Wintringham 1963, 1964). These expeditions described the sawgrass plains of the Everglades as vast, almost impenetrable and unfit for development. But development did come.

By 1930, four large canals had been constructed from Lake Okeechobee running southeastward and connecting with the Atlantic Ocean to provide drainage for agriculture. An additional canal had been cut from the west to connect with the Caloosahatchee River (Light and Dineen 1994). A major highway had been built from Naples on the southwest coast to Miami on the southeast and ran across the southern Everglades (Tebeau 1968). The resultant removal of water from this vast freshwater ecosystem had consequences for wetland plant communities and the animals that inhabited them (Gunderson 1994; Ogden 1994).

Calls for restoration of the Everglades date to the 1920s. J. K. Small (1929), for example, chronicled environmental degradation throughout south Florida, including the Kissimmee River - Lake Okeechobee - Everglades ecosystem, in his book entitled "From Eden to Sahara: A Story of Florida's Tragedy." In 1948, the U.S. Congress authorized the Central and Southern Florida Project to manage water resources in southern Florida for a variety of reasons including flood control, water supply and for the natural environment (4). CERP was authorized in 2000 as part of the Water Resources Development Act (5) in recognition that the natural system required restoration above and beyond earlier projects.

But to what state or condition do you restore an ecosystem? It is here that archival materials such as maps, charts and aerial photographs can prove invaluable, if they are indeed, saved, preserved and archived.

In August 1992 Hurricane Andrew, a Category 5 storm, crossed south Florida, impacting three United States National Parks: Everglades (ENP), Biscayne Bay and Big Cypress. Not only were natural ecosystems subjected to severe disturbance (Loope et al. 1994; Smith et al. 1994), but the Park's man-made infrastructures were also essentially destroyed. The visitors' centers for both Biscayne and Everglades National Parks needed to be bulldozed and totally rebuilt. In the aftermath of Hurricane Andrew, some of the present authors were studying the ecological consequences of the hurricane. While visiting ENP, and consulting with Park staff, we discovered that archives of aerial photographs and charts, both recent and historical, were not being maintained due to damage to the archive rooms and museum curatorial areas from the hurricane. In November 1995, we salvaged >25,000 individual aerial photographs, maps, charts and film canisters from Everglades NP and transported them to a U.S. Geological Survey laboratory in Gainesville, Florida where they could be safely stored while the Park was rebuilt.

Subsequent funding allowed us to begin scanning the materials into a permanent electronic format and the Everglades Historical Air Photo (EHAP) project was initiated (6). Additional funding has expanded the work and allowed us to begin using the digital information to address questions of ecosystem restoration, forecast potential impacts of climate change (e.g. sea level rise), inform management of endangered species and provide resource managers with crucial information to assist them with their responsibilities. In this chapter, we discuss the types of archival materials that we used, where they were found and how they were processed so they could be used. The primary purpose of our use of archival materials is to address questions of change: has change occurred, where change has occurred, how much change has occurred, what type of change has occurred, and what were (are) the drivers of the change? This last question is of prime importance for resource managers.