The composition of the U.S. Cabinet has evolved significantly since the country's founding, reflecting changes in governmental roles, priorities, and the expansion of federal responsibilities. Here’s an overview of how it has transformed over time:

 1. The Original Cabinet (1789)

   - Established by George Washington, the first U.S. Cabinet had only four departments:

     - Secretary of State (Thomas Jefferson)

     - Secretary of the Treasury (Alexander Hamilton)

     - Secretary of War (Henry Knox)

     - Attorney General (Edmund Randolph)

   - These positions were designed to handle the primary concerns of the new nation: foreign relations, finances, defence, and legal matters.

 2. 19th Century Additions

   - As the U.S. expanded geographically and economically, new departments were created to handle specialised areas:

     - Navy Department (1798) - Eventually merged with the Department of War to form the Department of Defense in 1947.

     Post Office Department (1829): Initially part of the Cabinet, it was reorganised as the independent U.S. Postal Service in 1971.

     The Department of the Interior (1849) was created to manage domestic issues such as Native American affairs, public lands, and natural resources.

     Department of Justice (1870): Although the Attorney General had existed since 1789, this formally established it as a department.

 3. Early 20th Century Expansions

   - Rapid industrialisation and progressive reforms led to further Cabinet expansion:

     - Department of Agriculture (1889) - Responded to the growing importance of farming.

     - Department of Commerce and Labor (1903) - Split in 1913 to create two separate departments as labour issues grew in importance:

       - Department of Commerce

       - Department of Labor

 4. Post-War and Modern Additions (20th Century)

   - With the New Deal, WWII, and the rise of modern government, several new departments were established to address the complex needs of a changing society:

     - Department of Defense (1947) - Merged the Department of War and the Department of the Navy, adding the newly created Air Force.

     - Department of Health, Education, and Welfare (1953) - Later split to form:

       - Department of Health and Human Services (1979)

       - Department of Education (1979)

     - Department of Housing and Urban Development (1965) - Focused on urban issues and housing.

     - Department of Transportation (1967) - Created in response to the need for federal transportation oversight.

     - Department of Energy (1977) - Addressed the importance of energy policy.

 5. Recent Additions and Homeland Security (21st Century)

   - The 21st century saw two new departments reflecting national security and veterans' needs:

     - Department of Veterans Affairs (1989) - Elevated to Cabinet status to address the growing needs of veterans.

     - Department of Homeland Security (2003) - Established in response to the 9/11 attacks, consolidating multiple agencies to protect against terrorism and manage border security.

 6. Cabinet-Level Positions Beyond Departments

   - In addition to department heads, other positions now hold Cabinet-level status:

     - U.S. Trade Representative

     - Director of National Intelligence

     - Ambassador to the United Nations

     - Director of the Office of Management and Budget

     - Administrator of the Environmental Protection Agency

     - Chair of the Council of Economic Advisers

     - Small Business Administration Administrator (sometimes included)

 Trends and Observations

   - Growth in Number: The Cabinet started with four members and has grown to more than 15 departments and various other Cabinet-level positions.

   - Specialization and Complexity: Cabinet positions reflect the specialisation required by a more complex society and government responsibilities.

   - Security and Welfare: Recent additions emphasise national security, welfare, and environmental concerns, aligning with modern priorities.

The record for the highest number of new members in the U.S. Congress was set during the 63rd Congress (1913–1915), when a large wave of new members joined following the election of 1912. This influx was mainly due to several unique factors:

1. Electoral Changes: The 17th Amendment, which established the direct election of senators, was ratified in 1913, leading to the election of new senators in several states.

2. Political Shifts: The 1912 election saw a significant split in the Republican Party. Former President Theodore Roosevelt ran as a Progressive (or "Bull Moose" candidate), which divided the vote and led to a Democratic landslide in Congress and the White House with the election of Woodrow Wilson. This shift brought many new members from both parties.

3. Territorial Changes: The addition of Arizona and New Mexico as states in 1912 also increased congressional representation.

During this period, he marked a unique transformation in Congress, with an influx of freshman senators and representatives, creating one of the most substantial turnovers in the history of the legislative body.

During the 63rd Congress (1913–1915), the Senate Majority Leader Thomas S. Martin (D-VA) and Vice President Thomas R. Marshall as the presiding officer led the Senate. However, the concept of a formal “majority leader” was not as established as today, and party leadership was more informal. Woodrow Wilson was president then, with Democrats holding the majority in both the Senate and the House.

Here’s a closer look at both key figures:

 Thomas S. Martin

Given his influence and seniority, Thomas Staples Martin of Virginia was considered the de facto leader of the Democrats in the Senate. However, he did not hold the title "majority leader" in the same sense it is understood today. Martin was a conservative Democrat and a proponent of states’ rights who often worked to unify his party behind important legislation.

Background and Accomplishments:

Early Life and Career: Martin was a Confederate veteran who served in the Civil War as a teenager. After the war, he studied law at the University of Virginia, which propelled him into a career in law and politics in Virginia.

- Political Influence: As a senior Democratic senator, he was influential in helping President Wilson pass landmark Progressive Era legislation, including the Federal Reserve Act and the Clayton Antitrust Act.

- Advocacy for States’ Rights: Martin often aligned with the South’s conservative bloc, opposing specific Progressive reforms that he felt overreached federal authority.

 Vice President Thomas R. Marshall

Thomas R. Marshall of Indiana served as Vice President and was technically the Senate’s presiding officer. He was a lawyer and the former governor of Indiana known for his wit and dry humour.

Background and Accomplishments:

- Early Life and Career: Marshall was a lawyer and served as the governor of Indiana from 1909 to 1913. His governorship was known for implementing progressive reforms, such as child labour laws and educational improvements.

- Role as Vice President: Although primarily ceremonial at the time, Marshall was known for his humorous remarks and amicable personality. He famously quipped, “What this country needs is a good five-cent cigar.”