Strength and deformation parameters of compacted soil are known to be related to soil type and moisture content. However, little attention has been directed towards understanding the influence of compaction energy on these properties. This paper describes laboratory and field studies conducted to evaluate the relationship between soil type, soil moisture content, and compaction energy on seven cohesive soil types. In the lab, specimens were compacted with impact energy at levels of 355, 592 (standard Proctor), 987, 1643, and 2693 kJ/m³ (modified Proctor) over a wide range of moisture contents to determine dry unit weight, unconfined compressive strength and the secant (50 percent strain) stiffness. In total, 175 Proctor tests and 95 unconfined compression tests were performed. At each energy level, a soil was tested at 4 to 5 moisture contents with respect to its standard Proctor moisture range. In addition, 54 consolidated undrained triaxial tests were performed at the five energies and four moisture contents for one soil to evaluate changes in effective stress shear strength parameters. This paper summarizes the results of statistical analyses performed on all lab and field tests conducted. The models that best explain variability in dry unit weight, strength, and stiffness are presented. Models are presented individually for each soil type and also inclusive of all soils grouped together. Independent variables used in the modeling include compaction energy, moisture content, confining pressure, Atterberg limits, material passing the No. 200 sieve, and clay fraction. In addition, a new compaction model, derived from a linear rate equation, is presented and checked for validity in estimating soil dry unit weight as a function of compaction energy. Results indicate that compaction energy, combined with moisture content, is a key factor in determining soil strength and stiffness parameters. It is concluded that the strength and stability of a compacted soil cannot be assessed in terms of relative compaction alone. Instead, this research encourages the use of strength and stiffness in the design and construction phases of earthwork operations, being the true functional requirements for compaction specifications.