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United States · IL

Alton Military Prison

State prisonFirst Illinois state penitentiary and Union prisonClosed 1865Medium
Verified 31 May 2026
Fresh · 1mo ago

Data is aggregated from public sources and may be incomplete or out of date. Always verify with primary sources before acting on any figure. See data sources.

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How to send mail, money, and visit Alton Military Prison

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Photograph of Alton Military Prison

Gallery

From Wikimedia Commons (CC-BY-SA where not otherwise stated).

  • Alton Military Prison Illinois.jpg

    Photo by Unknown authorUnknown author via Wikimedia Commons (Public domain)

  • Alton Military Prison remains.jpg

    Photo by Nyttend via Wikimedia Commons (Public domain)

  • Letter from George J. Mook, Alton Military Prison, Illinois, to his mother, December 10, 1864.jpg

    Photo by Mook, George J. via Wikimedia Commons (Public domain)

  • Letter from George J. Mook, Alton Military Prison, to his mother, November 29, 1864.jpg

    Photo by Mook, George J. via Wikimedia Commons (Public domain)

  • Letter signed P.S. Sandidge, Military Prison, Alton, Ill., to Mrs. Ada Haynes, March 6, 1862.jpg

    Photo by Sandidge, P.S. via Wikimedia Commons (Public domain)

Background

The Alton Military Prison was a prison located in Alton, Illinois, built in 1833 as the first state penitentiary in Illinois and closed in 1857. During the American Civil War, the prison was reopened in 1862 to accommodate the growing population of Confederate prisoners of war and ceased to be prison at the end of the war in 1865. The prison building was demolished not long after the Civil War. All that remains of the former prison site is a section of ruin wall that is maintained by the State of Illinois as an historic site. The prison site is included in the U.S. National Register of Historic Places.

Source: Wikipedia article lead, CC-BY-SA.

Capacity

1,833

Current population

—

Occupancy

—

Year opened

—

Closed 1865

Facility profile

Operator

Illinois Department of Corrections (1833-1857) Union Army (1862-1865)

Population held

Mixed/unknown

Opened

—

Region

IL

Security level

First Illinois state penitentiary and Union prison

Death-row facility

No

Conditions

No conditions summary available yet.

Visiting

No visiting information available.

Mailing

No mailing information available.

Practical info

Contact the operator's website for inmate-specific procedures.

Known issues

No major issues documented in our database.

Notable inmates

  • M. Jeff Thompson
    M. Jeff Thompson
    1826–1876 · engineer

    Brigadier-General Meriweather Jeff Thompson (January 22, 1826 – September 5, 1876), nicknamed "Swamp Fox," was an American soldier who was a senior officer of the Missouri State Guard who commanded cavalry in the Trans-Mississippi Theater of the American Civil War.

Source: Wikidata + Wikipedia.

Contact & address

Alton, Illinois, United States

No public contact details available.

Conditions Risk Score

Derived signal — not a judgement. How it's calculated

—
Insufficient data
We don't have enough public data on this facility to score it. Have something to add? Send us a correction.

Compared to other facilities in United States

7324 peers
Capacity (beds)this: 1833 · peers avg: 559 (+228%)

Data completeness

48%

How many of our profile fields are populated. We surface this so families and researchers know the limits.

Sources