FRAMEWORK The geomorphology of the Illinois-Indiana coastline developed in response to glacial processes that formed the lake margin and, subsequently, to coastal processes that modified the margin by erosion and accretion. The 156-km coast can be divided into three provinces. The northernmost is the Zion beach-ridge plain that extends from the Wisconsin border southward into Illinois as far as the city of North Chicago. This province is 19 km long, has a maximum width of 1 km and, stratigraphically, contains sediments as thick as 11 m. The second province, the Lake Border morainal- bluff coast, extends for 25 km from North Chicago to Winnetka. The shoreline has eroded into end moraines of the Lake Border Morainic Complex, which are as high as 30 m. The bluffs decrease in height southward in the third province, the Chicago/Calumet lacustrine plain, which rims the southern margin of the lake. This stretch of coastline extends 112 km from Winnetka, IL to the Indiana-Michigan state line. The relief extends from low lying areas near lake level to the Indiana Dunes which are as much as 50 m higher. Fifty-eight percent of all uplands along the Illinois-Indiana coast range from 0- 10 m in height. All of the Zion beach-ridge plain and most of the Chicago/Calumet lacustrine plain are no more than 5 m above the mean lake level. Compiled and interpreted maps of lake bottom sediment texture and stratigraphy show that most of the Illinois and Indiana nearshore area is a dynamic environment; currents, induced by storm waves, transport fine sand and silt, resulting in a patchy, continually changing distribution of lacustrine sediment overlying a till-gravel pavement. Only north of Waukegan and Michigan City does silty sand completely cover Wadsworth Till. The nearshore sand wedge is thickest north of Waukegan and thins southward to Chicago. Large volumes of sand offshore are limited to complex northeast-trending ridges formed at the outer margin of the sand wedge between Waukegan and Lake Forest. South of Lake Forest, the nearshore sand wedge is limited to within 300 m of the shoreline. Though several meters of sand are present in some areas of the bottom in Indiana Shoals, net erosion of the lake floor has taken place there over the last 20 years. West of Michigan City, the nearshore sand wedge is thin or absent. Thus, over much of the survey area, erosion or non- deposition has been taking place exposing the 10-40 m thick Wadsworth till or gravel-boulder lag deposits, and in some places the underlying Devonian shale or Silurian and Devonian carbonates. Sand has been diverted and entrapped by harbors and lakefills along the Illinois shore depleting the supply of littoral sands for longshore drift. Over 10,000,000 m3 of sand are present in the Waukegan Harbor sand fillet but much less is present in all the remaining lakefills surveyed as far south as Northwestern University. Comparisons of sand thickness in several areas south of Waukegan reveal that from 1975 to 1991 sand has been greatly depleted, exposing the underlying clay-rich till to erosion.