The Largest Jails in the United States

County jails anchor the front line of incarceration in the United States, cycling hundreds of thousands of people through their cells each year. Measured by average daily population, the largest jail in the US is the Los Angeles County Jail system, followed by Rikers Island in New York City, Harris County Jail in Texas, Cook County Jail in Illinois, and Maricopa County Jail in Arizona. Together with five other massive facilities, they concentrate an enormous share of the nation's jailed population in just a handful of counties.

Most people confined in these jails are awaiting trial or serving relatively short terms for local offenses, so decisions about policing, bail, and community supervision have direct, visible effects on their populations. These facilities cluster in large urban counties that serve as economic and cultural hubs, meaning their practices influence far more than the individuals in custody. Understanding where the biggest jails are, how large they are, and whom they hold provides a clear view of how local authority, budgets, and public safety priorities converge inside a small number of high-capacity detention systems.

The Largest Jails In The US

1. Los Angeles County Jail System - 19,836 Inmates

With nearly 20,000 people in custody on an average day, the Los Angeles County Jail system is the largest jail complex in the United States. Run by the Los Angeles County Sheriff's Department, it includes Men's Central Jail, the Twin Towers Correctional Facility, and several satellite sites. Most people held there are awaiting trial or serving short local sentences. Longstanding problems with overcrowding, mental illness, and use-of-force incidents have brought federal scrutiny and public pressure. In response, county leaders have pursued diversion programs, expanded medical and psychiatric services, and policies aimed at reducing jail use for low-level offenses.

2. Rikers Island - 13,849 Inmates

New York City's vast jail complex on Rikers Island ranks second on this list, holding an estimated 13,849 detainees. Situated in the East River between Queens and the Bronx, it is operated by the New York City Department of Correction and mainly confines people awaiting trial or serving short city sentences. For decades, Rikers has become a national symbol of violence, poor health care, and chaotic conditions, prompting lawsuits and federal oversight. City officials have adopted a long-term plan to shutter the island's facilities and replace them with smaller, borough-based jails designed to be safer and more modern.

2. Harris County Jail - 10,000 Inmates

In Houston, Texas, Harris County Jail functions as one of the country's largest pretrial detention centers, holding roughly 10,000 people on any given day. The Harris County Sheriff's Office oversees the complex, which also houses individuals serving short sentences or awaiting transfer to state prison. Persistent overcrowding, staffing gaps, and high rates of mental illness and substance use among detainees have strained the system. Local judges and policymakers have responded with bail reforms, diversion courts, and expanded treatment options. These changes are intended to curb the jail population while improving safety and basic living conditions behind bars.

4. Cook County Jail - 9,900 Inmates

Chicago's Cook County Jail, overseen by the Cook County Sheriff's Office, typically holds around 9,900 inmates and ranks fourth among the nation's largest jails. Located on a sprawling campus near the city's Southwest Side, it serves the busy Cook County criminal courts, confining primarily people awaiting trial and some serving short sentences. Over the years, the jail has drawn criticism for overcrowding, inadequate health care, and a heavy concentration of detainees with serious mental health needs. Recent initiatives have emphasized reforming bond practices, expanding electronic monitoring, and using diversion programs to keep lower-risk defendants out of custody.

5. Maricopa County Jail - 9,265 Inmates

In Phoenix, Arizona, the Maricopa County Jail system holds an estimated 9,265 inmates, making it the fifth-largest jail in the United States. The Maricopa County Sheriff's Office operates several facilities that together form the system. For many years it was known for the outdoor "Tent City" compound, closed in 2017 after widespread criticism of extreme heat and punitive conditions. The jails primarily confine people awaiting trial or serving short county sentences. Civil rights lawsuits and federal findings of unconstitutional practices have driven significant reforms focused on medical care, internal oversight, and establishing clearer minimum standards for living conditions.

6. Curran-Fromhold Correctional Facility - 8,811 Inmates

Opened in 1995, Curran-Fromhold Correctional Facility (CFCF) is the largest jail in Philadelphia's system and the sixth-largest in the nation, with an estimated population of 8,811 inmates. The facility, part of the Philadelphia Department of Prisons, serves as the city's main intake and reception center and can house roughly 2,000 people in multiple housing units. Most detainees are awaiting trial or serving short local sentences. Named for Warden Patrick Curran and Deputy Warden Robert Fromhold, killed at Holmesburg Prison in 1973, CFCF faces ongoing challenges related to crowding, staffing, and maintaining safety in a large urban jail environment.

7. Metro West Detention Center - 7,050 Inmates

In Miami, Florida, Metro West Detention Center stands as the largest facility in the Miami-Dade Corrections and Rehabilitation Department and the seventh-largest jail in the country. Its average population of about 7,050 consists mainly of adult men held at maximum, medium, or minimum custody levels. Most are pretrial detainees or serving short sentences of less than a year. Metro West has confronted recurrent concerns over crowding, security, and access to medical and mental health care. County officials stress an increasing focus on rehabilitation, offering educational, vocational, and reentry programs designed to reduce recidivism and ease the transition back to the community.

8. Dallas County Jail - 6,385 Inmates

Crowding the skyline of downtown Dallas, the Dallas County Jail complex forms one of the nation's largest county detention systems, ranking eighth on this list with about 6,385 inmates. Managed by the Dallas County Sheriff's Department, the interconnected facilities house people awaiting trial in county courts, as well as those serving short sentences or awaiting transfer to state custody. The system has struggled with overcrowding and the demands of providing adequate medical and mental health care to a large and diverse population. In response, the county has expanded diversion courts, treatment initiatives, and reentry programs to ease pressure on the jail.

9. Orange County Jail - 6,000 Inmates

The Orange County Jail system in California, operated by the Orange County Sheriff's Department, typically holds around 6,000 detainees, placing it ninth among the largest jails in the United States. Its major facilities include the Intake Release Center and Central Men's and Women's Jails in Santa Ana, along with the sizable Theo Lacy Facility in Orange. The system mainly confines pretrial detainees and individuals serving short county sentences. In-custody deaths, questions about medical care, and concerns over use-of-force practices have spurred lawsuits and external investigations, prompting ongoing efforts to strengthen oversight and improve conditions for people held there.

10. Shelby County Jail - 5,765 Inmates

Known locally by its downtown address, 201 Poplar, Shelby County Jail in Memphis, Tennessee, rounds out the top ten with an estimated 5,765 inmates. The Shelby County Sheriff's Office runs the facility, which holds people awaiting trial in county criminal courts and some serving short local sentences. As in many large urban jails, overcrowding, limited staffing, and a high proportion of detainees with mental health and substance use disorders pose persistent challenges. Recent reforms and legal actions have targeted improvements in medical and mental health services, upgrades to basic conditions, and the use of alternative programs to reduce incarceration.

Viewed together, the largest jails in the United States show how much power over incarceration is concentrated in a small number of counties. Los Angeles County, New York City, Harris County, Cook County, Maricopa County, and their peers manage populations comparable to small towns, mostly made up of people awaiting trial. Their size magnifies every decision about policing, bail, treatment, and reentry.