I examine the development of privately provided insurance since World War II, giving special attention to Empire Blue Cross, and argue that the competition between employers and unions for the loyalty of workers after the passage of the Taft-Hartley Act helped diffuse private health insurance benefits already favored by federal policies. For-profit insurers did not challenge the privileged status of Blue Cross plans because they recognized the political benefits that the plans offered and because they did not wish to offend the plans' sponsors. A relatively easy and profitable business, health insurance has been greatly disturbed by the system inflation accompanying the introduction of Medicare and Medicaid programs. Now self-insurance and various managed-care schemes are major threats. The future may bring consolidation and the strengthening of pools, just the opposite of today's system fragmentation.