The United States Capitol Police has the primary responsibility for protecting life and property, preventing, detecting, and investigating criminal acts, and enforcing traffic regulations throughout a complex of congressional buildings, parks, and thoroughfares.

Officers also have jurisdiction throughout the District of Columbia to take enforcement action when they observe or are made aware of crimes of violence while on official duties.

While performing protective functions, the Capitol Police have jurisdiction throughout the entire United States.

In the early 1980s, the protective mandates and jurisdictions of the U.S. Capitol Police were substantially expanded to allow them to protect legislators away from their normal jurisdictions in response to the growing risk and threats faced by legislators and the growing institutionalization of Congress.

[8] The U.S. Capitol Police also have extended jurisdiction over parts of Northeast, Northwest, and Southwest Washington D.C.[9] The USCP provides protection detail to House and Senate leaders, other congressmen and -women depending on individual risk analysis, lawmakers' state and district offices (with the help of local police), and "off-campus" events such as presidential nominating conventions.

[11] The chief is “whipsawed between partisan politicians and career professionals like the two Sergeants at Arms and congressional staff...here they literally have hundreds of people who think they're their bosses.

[12] In FY 2021, the USCP had an annual budget of more than $515 million;[2] it employs more than 2,000 sworn and civilian personnel, making it one of the most well-funded and well-staffed police departments relative to the two square miles it guards.

After the recruits' academy training, graduates are sworn in as law enforcement officers and assigned to one of four divisions to begin their careers.

[17] The U.S. Capitol Police is organized into bureaus and offices that report to each of the executive team members.

[22][23] The history of the United States Capitol Police dates back to 1801 when Congress moved from the city of Philadelphia to the newly constructed Capitol Building in Washington, D.C. At the time, Congress appointed one watchman to protect the building and Congressional property.

These services are provided through the use of a variety of specialty support units, a network of foot and vehicular patrols, fixed posts, a full-time Containment and Emergency Response Team (CERT), K-9, a Patrol/Mobile Response Division and a full-time Hazardous Devices and Hazardous Materials Sections.

[27][28] In 2005 Congress established the United States Capitol Police (USCP) Office of Inspector General (OIG) as a legislative agency.

The inspector general heads OIG, supervises and conducts audits, inspections, and investigations involving USCP programs, functions, systems, and operations, and reports directly to the Capitol Police Board.

[35]) At a rally in Washington on January 6, 2021, Trump's lawyer Rudy Giuliani called for "trial by combat".

Ultimately, one unarmed woman, Ashli Babbitt, was fatally shot by a USCP officer when she attempted to climb through a shattered window in a barricaded door, and three other rioters died in medical emergencies.

[49][40][50][51][52] Law enforcement was urged "to avoid the type of show of force that had inflamed tense situations in the city last year.

"[40] At the behest of the speaker of the House of Representatives, Capitol Police chief Steven Sund announced his resignation the following day, effective January 16, 2021.

[60] Due to threats and other security measures in the wake of the 2021 United States Capitol attack, the agency announced plans to open field offices in California and Florida on July 6.