Cable-actuated manipulators possess a number of unique properties, which can have complex effects on their wrench-exertion and stability characteristics. Consequently, their useful workspaces are often unknown or irregularly shaped, so such robots are typically restricted to operate in unnecessarily small, conservatively estimated workspaces. To describe this "useful" workspace, this paper introduces the force-feasible workspace (FFW), defined as the set of end-effector poses for which static equilibrium is maintained and all of a set of required wrenches can be exerted on the environment. Next, this paper presents a means for analytically deriving this region for the case of a point-mass end-effector, which has been validated via numerical simulation. Characteristics and trends of the FFW are observed and analyzed, and correlations between robot design parameters and observed workspace properties are determined. The analysis presented here is a valuable tool for the design of cable robots with optimized workspace properties.