What organization was founded by CIGNA in 1966 primarily for managing workers' compensation?

The organization founded by CIGNA in 1966 primarily for managing workers' compensation is Intracorp. This company was established to specialize in the management of workers' compensation and disability claims, providing services that include medical case management, vocational rehabilitation, and injury prevention. Intracorp has a strong focus on facilitating the return-to-work process and optimizing health outcomes for injured workers, which aligns with CIGNA's broader mission of health management.

The other options are not associated with CIGNA in this specific context. For instance, Amerigroup focuses on managed healthcare services, particularly for individuals who are eligible for Medicaid. MedCost operates in the area of employee benefits and health plan management but does not have the same historical roots in worker’s compensation as Intracorp. HealthNet, on the other hand, is known for its health insurance products and services but is not linked to the founding of an organization for workers’ compensation management by CIGNA. Thus, Intracorp stands out as the correct answer due to its direct connection to CIGNA and its specialization in the worker's compensation domain.