The construction of highways over compressible ground produces some of the difficult problems in soil mechanics. When highway construction was relatively small, “rule of thumb” and dependence upon individual personal experience were reasonably adequate; however, with expansion of highway construction into the biggest construction project of all time, problems have increased in importance. High-speed, wide freeways extending into areas where low-speed, narrow roadways had previously been adequate places greater emphasis on the rational soil mechanics methods. The best use of these methods depends upon observations on the behavior of projects already designed and constructed. In this way evaluations and improvements on these methods can be made. The present paper is focused upon foundation subsidence, primarily as it produces losses in elevation and nonuniformity of grade. Several highway projects in the California State Highway System are described. Typical foundation soils data are summarized for each project, the foundation treatment method is described, and project settlement records are presented. The projects represent a wide range of soil conditions and periods of record up to 40 yr.