Medicare was signed into law on July 30, 1965, and within a year, seniors were receiving coverage. President Barack Obama signed the Affordable Care Act on March 23, 2010, and the uninsured start getting coverage more than three years later, on Jan. 1, 2014.
Some key dates in the saga of Obama's signature legislation:
March 23, 2010 — Obama signs the Patient Protection and Affordable Care Act, known commonly as the Affordable Care Act. The law requires most Americans to have health insurance starting in 2014, and bars insurers from turning away the sick. It creates state markets for middle-class people without workplace coverage to purchase private insurance, subsidized with tax credits. It expands Medicaid (in some states) for the low-income uninsured. After long debate, the legislation barely passed a divided Congress, with no Republican support. Public opinion is split.
March 29, 2010 —Health and Human Services Secretary Kathleen Sebelius and the health insurance industry reach a deal to fix the first glitch emerging from the complex legislation: vague language that compromised a guarantee that children with pre-existing medical conditions could get coverage right away.
Fall 2010 — During open enrollment, most health insurance plans begin offering coverage to young adults up to age 26 on a parent's policy. The popular early provision expanded coverage to more than 3 million people. Plans also begin covering preventive services at no charge.
Nov. 2, 2010 — Democrats lose control of the House in midterm congressional elections. Republicans campaigned on a vow to "repeal and replace" the law.
Jan. 19, 2011 — The Republican-led House votes to repeal what they call "Obamacare," but the drive falters in the Senate, where Democrats retain a majority. Since then, the House has repeatedly voted to repeal, defund or in some way scale back the law.
Jan. 31, 2011 — Florida U.S. District Judge Roger Vinson rules that the ACA is unconstitutional. The lawsuit by 26 states would ultimately reach the Supreme Court.
April 5, 2011 — Congress votes to repeal an unpopular tax requirement in the law that would have forced millions of businesses to file tax forms for every vendor selling them more than $600 in goods. Obama signed the law.
June 21, 2011 — The Obama administration says it will look to fix a twist that would have let several million middle-class people receiving Social Security payments get nearly free insurance meant for the poor. That fix saved an estimated $13 billion over 10 years.
Summer 2011 — Seniors hitting Medicare's prescription drug coverage gap start getting a 50 percent discount on brand name medications, part of the health care law's gradual closing of the "doughnut hole." In 2011, the typical senior in the gap saved about $600 on bills averaging $1,500.
Aug. 1, 2011 — Sebelius extends most health plans must cover birth control for women as a free and preventive service. (The coverage became available in 2013, as lawsuits proliferated from groups and businesses objecting on religious grounds.)
Oct. 14, 2011 — Sebelius pulls the plug on the ACA's long-term care insurance program, because of doubts over its long-term financial solvency.
Nov. 14, 2011 — The Supreme Court announces it will hear the constitutional challenge to the ACA.
Fall/Winter 2011-2012 — Republican presidential candidates are united in their determination to repeal "Obamacare."
March 26-28, 2012 — The Supreme Court holds three days of oral arguments on the ACA.
June 28, 2012 — With the unlikely support of conservative Chief Justice John Roberts, the Supreme Court upholds the law's core requirement that most Americans have health insurance, ruling that the penalties to enforce it are a tax Congress is authorized to levy. But the court allows states to individually opt out of the Medicaid expansion.
Summer 2012 — Employers and consumers receive more than $1 billion in rebates from insurers, which are required under the ACA to spend at least 80 cents of every premium dollar on medical expenses and quality improvement, or refund the difference.
Nov. 6, 2012 — Obama is re-elected to a second term, deflating Republican repeal hopes.
Jan. 1, 2013 — Tax increases to finance the ACA take effect on about 2.5 million households, individuals making more than $200,000 per year and couples over $250,000.
Winter/Spring, 2013 — States decide whether they'll run the new insurance markets and expand Medicaid programs.
April 30, 2013 — The Obama administration unveils simplified forms that consumers will use to apply for health insurance and financial assistance to pay premiums after the first version was criticized as too complicated.
July 2, 2013 — In a surprise, the White House announces a one-year delay — until 2015 — of the law's requirement that companies with 50 or more workers must provide affordable coverage or pay fines. The administration says it's trying to iron out burdensome reporting requirements.
Oct. 1, 2013 — Online insurance markets are scheduled to open in every state. Consumers must sign up by Dec. 15 for coverage to take effect Jan. 1.