The person at the center of this case
Mark Bonner
Missing Person · Open
48 years waiting · since 1978
Missing Person: Mark Bonner
Justice for Mark Bonner — the trail went cold in 1978, but the truth hasn't.
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Key leads to think about
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person
Lead #1What was Mark Bonner's daily routine and who were his close associates in Boulder in March 1978?
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timeline
Lead #2Were there any significant events or conflicts in Mark's life immediately before his disappearance?
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witness
Lead #3Did anyone see Mark on or after March 20, 1978, or notice anything unusual about his activities?
Mark Bonner, a 23-year-old white male, disappeared in Boulder, Colorado on March 20, 1978, and has never been found. The circumstances of his disappearance remain unclear, with no confirmed sightings or leads in the decades since. Anyone with information about Mark's whereabouts or what happened to him is urged to contact the Boulder County Sheriff's Office.
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More leads to consider
Beyond the top three above — each detail below could be the thread that pulls this case open.
💡
clue
Lead #4Why did Mark disappear without a trace, and are there any unidentified remains that might be connected to this case?
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Even the smallest detail could be the key to solving this case.
Official wording
Source Narrative
NamUs case MP25589. Missing person: Mark Bonner.
Last known contact: 1978-03-20 in Boulder, Boulder, CO. Circumstances: Mark Bonner was last seen in Boulder, CO on March 20, 1978.
Demographics: 23 years, Male, White / Caucasian. Physical description: 6 ft 3 in, 150 lbs, hair: Blond/Strawberry, eyes: Blue.
Investigating agency: Boulder County Sheriff's Office | 78-3741.
Timeline of Events
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1978-03-20
Last Seen
Mark Bonner was last seen in Boulder, Colorado on March 20, 1978.
Key Locations
Interactive map showing important locations related to this case
Case Information
Incident:March 20, 1978
Last Updated:June 10, 2026
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Any information, no matter how small, could be crucial to solving this case.
Phone: 3034413600
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Case Information
Incident:March 20, 1978
Last Updated:June 10, 2026
Have Information?
Any information, no matter how small, could be crucial to solving this case.
Phone: 3034413600
You can remain anonymous