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
👁️
witness
Lead #1Were there any witnesses who saw Mark Bonner on or around March 20, 1978 in Boulder?
💡
clue
Lead #2What were the circumstances surrounding his disappearance and why did he vanish without a trace?
👤
person
Lead #3Did Mark have any known associates, friends, or acquaintances in Boulder at the time of his disappearance?
Mark Bonner, a 23-year-old white male, disappeared in Boulder, Colorado on March 20, 1978, and has never been found. Standing 6'3" with distinctive blonde hair and blue eyes, he vanished without explanation nearly 50 years ago. Despite the passage of time, investigators continue to seek information about the circumstances of his disappearance and any potential witnesses who may have encountered him.
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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
👁️
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 12, 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 12, 2026
Have Information?
Any information, no matter how small, could be crucial to solving this case.
Phone: 3034413600
You can remain anonymous