Sources
(1) Tufts Managed Care Institute, "A Brief History of Managed Care" 

(2) Kaiser Permanente "History of Kaiser Permanente" 

(3) Blue Cross Blue Shield Association "Blues History" 

(4) Centers for Medicare and Medicaid Services "Key Milestones in CMS Programs" 

(5) California Health Care Foundation "Making Sense of Managed Care Regulations in California" 

(6) MCOL Managed Care Fact Sheets 
(7) NCQA Timelines

TimeLine

1917
Western Clinic in Tacoma provides prepaid physician services for the lumber industry (3)

1929
Dr. Justin Ford Kimball at Baylor Hospital in Texas establishes The Baylor Plan, a prepaid hospitalization plan that first uses the Blue Cross logo (3) 

Ross-Loss prepaid medical clinic started by Drs. Donald Ross and H. Clifford Loos under contract with Los Angeles Department of Water and Power for its employees (1) 

Rural Farmers' Cooperative Health Plan started by Michael Shadid in Elk City, OK (1)

1933
Sidney Garfield MD establishes prepaid plan to fund care for his Contractors General Hospital and clinic providing care to workers on Los Angeles Aqueduct (2) 

1937
Group Health Association (GHA) started in Washington, DC to serve employees of Federal Home Loan Bank (1)

1938
Henry J Kaiser recruits Dr. Garfield to establish prepaid clinic and hospital care for his Grand Coulee Dam project in Washington (2) 

1939
Blue Shield program adopted for participating prepaid physician plans (3)

1942
At the request of Henry Kaiser, Dr. Garfield expands program to Kaiser-managed shipyards and Kaiser steel mill (2)

1945
Group Health Cooperative of Puget Sound established in Seattle, WA (1)
 
Permanente Health Plans opens to the public in California, in addition to serving Kaiser employees (2) 

1947
American Medical Association (AMA) indicated and convicted of antitrust violations due to organized efforts to curb physician participation with Group Health Plans (1) 

Health Insurance Plan (HIP) of Greater NY established to serve NY city employees (1)

1949
81 Blue Cross hospital Plans and 44 Blue Shield medical Plans cover 24 million Americans (3)

1952
Permanente Health Plans changes name to Kaiser, while medical group retains Permanente name. Kaiser membership at 250,000 (2) 

1954
First IPA formed, the San Joaquin Medical Foundation, in California (1)

1955
Kaiser expands to Oregon and total membership reaches 500,000 (2)

1958
Kaiser expands to Hawaii (2)

1959
Blue Cross Companies cover 52 million and Blue Shield Plans cover 40 million Americans (3)

1963
Kaiser membership reaches 1 million (2)

1968
Kaiser expands to Colorado and Ohio (2)

1970
Paul Ellwood coins the term "Health Maintenance Organization" (1)

1973
HMO Act of 1973 signed into law by President Nixon, using federal funds and policy to promote HMOs (1)

1976
Kaiser membership reaches 3 million (2)

1979
Blue Cross Blue Shield collectively covers 87.4 million Americans (3)

1980
Kaiser expands to Mid-Atlantic region (2)

1981
Kaiser membership reaches 4 million (2) 

1982
California legislation enacted allowing selective contracting for Medicaid and private insurance, paving the way for other states to enact similar laws facilitating Preferred Provider Organizations (PPOs) (5) 

The Tax Equity and Fiscal Responsibility Act (TEFRA) made it easier and more attractive for HMOs to contract with the Medicare program. (4) 

1985
National total HMO enrollment reaches 19.1 million (6)

1990
National total HMO enrollment reaches 33.3 million (6)

National PPO enrollment surpasses HMO enrollment with 38.1 million
members (6)

NCQA established (7)

1991
HEDIS 1.0 released (7)

1994
Blue Cross Blue Shield Association eliminates requirement that all Member Plans must maintain not-for-profit status (3) 

1995
National total HMO enrollment reaches 50.6 million (6) 

1996
Health Insurance Portability & Accountability Act of 1996 (HIPAA) includes patient privacy compliance and health plan portability provisions (4)

1999
NCQA initiates accreditation of PPOs, which now cover 89 million
Americans (7)

2000
National total HMO enrollment is 80.9 million, declining for the first time from the previous year's level (81.3 million in 1999) (6) 

2003
Medicare Modernization Act establishes Part D drug benefit, establishes HSAs, renames Medicare+Choice program to Medicare Advantage and increases payment rates to Medicare Advantage plans (4) 

2004
National total HMO enrollment is 68.8, and national PPO enrollment is 109 million (6)

2006
National total HMO enrollment is 67.7, and national PPO enrollment is 108 million (6) Medicare Part D prescription benefit becomes effective.