Landmark Laws That Shaped America

Reference · Understanding American Government

In brief: A federal law is created when the House and Senate pass identical text and the president signs it, or when Congress overrides a veto by a two-thirds vote in each chamber. A small number of these laws, from the Judiciary Act of 1789 to the 2025 budget reconciliation law, reshaped how Americans work, vote, retire, get health care and relate to their government. This page explains the process, lists 26 landmark laws in one table, and looks at why some of them became part of voters’ political identities.

How does a bill become a law?

Any member of Congress can introduce a bill, though bills that raise revenue must start in the House of Representatives. The bill goes to a committee, which can hold hearings, amend it (“markup”) or let it die. If the committee approves it, the full chamber debates and votes on it. A simple majority is needed to pass.

The other chamber then takes up the bill. Both the House and Senate must pass exactly the same text. When their versions differ, the chambers either trade amendments back and forth or appoint a conference committee of members from both sides to write a compromise, which each chamber must then approve.

The final bill goes to the president, who has three main options:

• Sign it, and it becomes law.
• Veto it and return it to Congress with objections. Congress can override the veto with a two-thirds vote in both the House and Senate.
• Take no action. If Congress is in session, the bill becomes law after 10 days (Sundays excepted) without a signature. If Congress has adjourned and the president does not sign, the bill dies, which is called a “pocket veto.”

Presidents can also shape policy without Congress through executive orders, which are explained in our guide to executive orders. Agreements with other countries follow a separate path, covered in treaties and international agreements.

What are the filibuster and budget reconciliation?

In the Senate, debate generally continues until senators vote to end it. Ending debate, called cloture, requires three-fifths of all sworn senators, usually 60 votes, a threshold the Senate set in 1975 after first adopting a cloture rule in 1917 (U.S. Senate). In practice this means most major bills need 60 votes in the Senate, not 51. As of October 2026, the 60-vote threshold still applies to most legislation, although the Senate has lowered it for nominations. Budget reconciliation is the main exception: created by the Congressional Budget Act of 1974, it lets bills that change spending, revenue or the debt limit pass the Senate by a simple majority with limited debate, but the “Byrd rule” bars provisions that are mainly unrelated to the budget. Several laws in the table below, including the 2025 tax-and-spending law, were passed this way.

Which laws are considered landmarks?

Historians and the National Archives tend to name the laws below because they created lasting institutions, extended rights or changed the relationship between citizens and the federal government. Many appear in the National Archives’ list of milestone documents. Dates are the day the law was enacted.

A note on the 2025 law: its official title is “An act to provide for reconciliation pursuant to title II of H. Con. Res. 14” (GovInfo). It passed as H.R. 1 and is widely known by the name its sponsors gave it, the One Big Beautiful Bill Act. Among other provisions, it allows deductions for tips and overtime pay through 2028, adds a deduction for people 65 and older, adds Medicaid work requirements for some adults and raises the debt limit by $5 trillion (Rehmann; USAFacts). Many provisions phase in through 2028, so its full effects are still unfolding.

Why was the Social Security Act so important?

Franklin D. Roosevelt signed the Social Security Act on August 14, 1935, during the Great Depression (Social Security Administration). Workers and employers paid payroll taxes, and retirees received benefits based on their earnings. The first recurring monthly check, for $22.54, went to Ida May Fuller of Vermont in January 1940 (SSA).

The program has since grown to include disability insurance and benefits for survivors. More than 71 million people receive Social Security benefits, according to a Congressional Research Service summary of the 2026 Trustees Report. That report projects the combined retirement and disability trust funds will be depleted in 2034, after which incoming taxes would cover only part of scheduled benefits unless Congress acts (CRS).

What did the Civil Rights Act and Voting Rights Act change?

The Civil Rights Act of 1964 ended legal segregation in hotels, restaurants, theaters and other public accommodations. Title VII banned job discrimination based on race, color, religion, sex or national origin and created the Equal Employment Opportunity Commission. It became law after the Senate broke a filibuster that lasted for weeks.

The Voting Rights Act of 1965 banned discriminatory voting practices such as literacy tests in covered areas. Its Section 5 required jurisdictions with histories of discrimination to get federal approval, called “preclearance,” before changing election rules. Voter registration among Black Southerners rose sharply in the years that followed.

Courts have since narrowed the law. In Shelby County v. Holder (2013), the Supreme Court struck down the formula that decided which places needed preclearance, effectively ending that requirement. On April 29, 2026, in Louisiana v. Callais, the Court ruled 6–3 that Section 2 of the act did not require Louisiana to draw a second majority-Black congressional district, and held the state’s race-based map unconstitutional (Faegre Drinker). For how public trust in the Court has shifted, see our commentary on Supreme Court trust.

How did Medicare and Medicaid change health care?

Lyndon B. Johnson signed the Social Security Amendments of 1965 on July 30, 1965, creating Medicare and Medicaid. Medicare is a federal health insurance program for people 65 and older, later extended to many younger people with disabilities. Medicaid is run jointly by the federal government and the states and covers people with low incomes.

Before 1965, many older Americans had no health insurance. As of April 2026, Medicare covered about 70.3 million people, according to federal enrollment data reported by ACA Signups. Medicaid is now the largest source of coverage for low-income Americans and a major payer for nursing-home care.

What has the Affordable Care Act done?

The Affordable Care Act, signed by Barack Obama on March 23, 2010, required insurers to cover people with pre-existing conditions, let young adults stay on a parent’s plan until 26 and created state insurance marketplaces with income-based subsidies. It also offered federal funding for states to expand Medicaid to more low-income adults.

The Supreme Court made the Medicaid expansion optional for states in 2012. As of October 2026, 41 states, including the District of Columbia, have adopted the expansion and 10 have not (KFF). Enhanced marketplace subsidies first enacted in 2021 expired at the end of 2025, and 2026 marketplace sign-ups fell to about 23.1 million, down more than a million from 2025 (KFF).

Why do landmark laws become identity issues for voters?

Major laws often start as partisan fights and end up as part of how people see themselves. Psychology offers several explanations, covered more broadly in our guide to political psychology.

• Loss aversion. In their 1979 paper on prospect theory, Amos Tversky and Daniel Kahneman found that people’s reactions are steeper for losses than for equivalent gains (Econometrica). Once a benefit exists, cutting it is felt as a loss, which is one reason established programs are hard to scale back.
• Status quo bias. William Samuelson and Richard Zeckhauser showed in 1988 that people choose the existing option disproportionately, even in important decisions such as health and retirement plans (Journal of Risk and Uncertainty).
• Policy feedback. Political scientist Andrea Louise Campbell found that Social Security helped turn older Americans from one of the least politically active age groups into one of the most active, and that engaged seniors then defend the program (Princeton University Press). Laws can create the very constituencies that protect them.

These patterns cut across parties. Voters may defend a program they once opposed, and people who feel a law threatens their status or values may oppose it strongly for years. For more commentary on how this plays out in elections, see the politics hub. For the presidents who signed these laws, see our history of American presidents.

Key takeaways

• A bill becomes law when both chambers pass identical text and the president signs it, or when Congress overrides a veto by two-thirds in each chamber.
• The Senate’s 60-vote cloture rule shapes most major legislation; budget reconciliation lets some tax and spending bills pass by simple majority.
• Landmark laws such as Social Security (1935), the Civil Rights Act (1964), the Voting Rights Act (1965), Medicare and Medicaid (1965) and the Affordable Care Act (2010) created institutions millions of people rely on today.
• Many landmark laws keep changing through amendments, court rulings and later laws, including the 2026 Louisiana v. Callais decision and the 2025 reconciliation law.
• Loss aversion, status quo bias and policy feedback help explain why established laws become part of voters’ identities and are hard to repeal.

More in Understanding American Government

• The American Presidents: A Short History of the Office
• Executive Orders Explained: What They Are and How They Work
• Presidential Approval Ratings Through History
• Treaties and International Agreements: How the U.S. Makes Them

Sources

• Filibuster and Cloture — U.S. Senate
• Milestone Documents — National Archives
• Public Law 119-21 — GovInfo, U.S. Government Publishing Office
• Presidential Statement Signing the Social Security Act — Social Security Administration
• Social Security: Selected Findings of the 2026 Annual Report — Congressional Research Service
• Supreme Court Decides Louisiana v. Callais — Faegre Drinker
• Status of State Medicaid Expansion Decisions — KFF
• What We Know So Far About 2026 ACA Marketplace Enrollment — KFF
• Prospect Theory: An Analysis of Decision under Risk — Econometrica
• Status Quo Bias in Decision Making — Journal of Risk and Uncertainty

Part of the brossi.us reference library, written for readers of Dr. Bart Rossi, PhD. Last reviewed October 2026.