Overview

Last seen: December 10, 2022
Location: Mason, Bayfield County, Wisconsin
Age when missing: 53
NamUs #: MP117473
Law enforcement case #: B1-23-099
Investigating agency: Bayfield County Sheriff’s Office

Main circumstances: Marc was last known to be in Mason, Wisconsin, on December 10, 2022. Public missing-person information provides few details about what happened immediately before or after his disappearance. His clothing at the time he went missing has not been publicly identified. Authorities have noted that Marc has ties to Montana.

Detailed Case Breakdown

Marc Duane Arthun Missing from Mason, Wisconsin Since December 2022

Marc Duane Arthun was 53 years old when he disappeared from Mason in Bayfield County, Wisconsin, in December 2022. More than three years later, his case remains publicly listed as a missing-person case, with authorities continuing to seek information that could help determine what happened to him.

Very Brief Case Summary

Last seen: December 10, 2022
Location: Mason, Bayfield County, Wisconsin
Age when missing: 53
NamUs #: MP117473
Law enforcement case #: B1-23-099
Investigating agency: Bayfield County Sheriff’s Office

Main circumstances: Marc was last known to be in Mason, Wisconsin, on December 10, 2022. Public missing-person information provides few details about what happened immediately before or after his disappearance. His clothing at the time he went missing has not been publicly identified. Authorities have noted that Marc has ties to Montana.

The Disappearance of Marc Duane Arthun

Marc Duane Arthun was last known to be in Mason, a community in Bayfield County in northern Wisconsin, on December 10, 2022. He was 53 years old at the time.

Public missing-person records describe Marc as a white male standing approximately 5 feet 11 inches tall and weighing between 210 and 220 pounds. He has hazel eyes and gray or partially gray hair. He has also worn a long beard, although his appearance could have changed considerably during the years since he was last seen.

Few Details Are Publicly Available About His Last Known Movements

One of the difficulties surrounding Marc’s disappearance is the limited amount of publicly released information about the circumstances of his last contact.

Available case information identifies Mason, Wisconsin, as the place from which he disappeared and December 10, 2022, as his date of last contact. Public case summaries do not identify what clothing Marc was wearing, where specifically in the Mason area he was last seen, who last had contact with him, whether he was traveling in a vehicle, or what his intended destination may have been.

That lack of publicly available detail leaves a significant gap between Marc’s last known contact and the subsequent missing-person investigation.

Marc Has Ties to Montana

Investigators and missing-person organizations have specifically noted that Marc has ties to Montana. This detail could be important because someone who encountered him after December 2022 may associate him with Montana rather than Wisconsin.

Marc’s documented history confirms substantial connections to Montana. Federal court records from an earlier, unrelated criminal proceeding identify him as Marc Duane Arthun and show that he had been involved in the Montana justice system years before his disappearance.

Those older records provide background confirming his Montana connections but do not, by themselves, establish what happened to Marc after December 10, 2022.

What Does Marc Arthun Look Like?

At the time of his disappearance, Marc was described as approximately 5 feet 11 inches tall and weighing between 210 and 220 pounds.

He has hazel eyes and gray or partially gray hair. Photographs circulated in missing-person materials show Marc with facial hair, and authorities advise that he may have a beard.

Because several years have passed since his disappearance, his current appearance could differ from the photographs being circulated.

Investigation and Current Case Status

The Bayfield County Sheriff’s Office is the law enforcement agency associated with Marc’s missing-person investigation. Publicly circulated case information identifies the agency’s case number as B1-23-099.

Marc is also entered into the National Missing and Unidentified Persons System under NamUs case MP117473.

As of September 2026, current publicly accessible missing-person resources continue to identify Marc as missing. Recent searchable listings still give December 10, 2022, as his last-seen date and Mason, Wisconsin, as his last known location.

A Wisconsin Missing article published in April 2025 renewed attention to the case and directed anyone with information to the Bayfield County Sheriff’s Office. CaseTrace also continues to maintain a published missing-person flyer for Marc connected to his NamUs record.

No reliable public source located during the latest review announced that Marc had been found, identified a confirmed later sighting, disclosed an arrest connected with his disappearance, or announced that his disappearance had been reclassified as a homicide.

Online Discussion and Unverified Leads

Marc’s disappearance has also received attention from online missing-person communities.

A Websleuths discussion created in December 2024 collected his publicly available case information, including his last-contact date, Montana ties, NamUs entry and Bayfield County Sheriff’s Office case number.

Other online discussions have attempted to identify possible destinations or places Marc may have traveled. One Reddit compilation, for example, included speculation that he might have gone to Wyoming. That claim should not be treated as a confirmed sighting or established investigative fact. No reliable law-enforcement or official missing-person source located during this review publicly confirms that Marc reached Wyoming after leaving Wisconsin.

Online discussion can sometimes generate useful leads, but information posted in comments or discussion forums should be provided directly to investigators so that law enforcement can determine whether it is credible.

The Search for Answers Continues

Marc Duane Arthun has now been missing since December 10, 2022. Despite the passage of time, his publicly available case remains active in missing-person databases and awareness resources.

The central unanswered question remains simple: what happened to Marc after his last known contact in Mason?

Someone may remember seeing Marc, communicating with him, giving him a ride, encountering him while traveling, or hearing him discuss plans to leave Wisconsin. Information that seemed insignificant at the time could help investigators reconstruct his movements.

Anyone with information concerning Marc Duane Arthun’s disappearance should contact the Bayfield County Sheriff’s Office at 715-373-6300. The department also maintains a tip line at 715-373-6197 and a non-emergency dispatch number at 715-373-6120.