# Relationship history for MSHA mine 4800900

Current hierarchy: **Arch Resources Inc → Arch Of Wyoming LLC → Medicine Bow Mine**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Ashland Inc et al → Medicine Bow Mine; 1950-01-01 to 2006-04-04; source msha-controller-operator-history
- **operator_operates_mine:** Medicine Bow Coal Company → Medicine Bow Mine; 1974-02-01 to 1989-02-28; source msha-controller-operator-history
- **controller_controls_mine:** Arch Mineral Corp & Rocky Mountain Energy → Medicine Bow Mine; 1974-02-01 to 1989-02-28; source msha-controller-operator-history
- **controller_controls_operator:** Arch Mineral Corp & Rocky Mountain Energy → Medicine Bow Coal Company; 1974-02-01 to 1989-02-28; source msha-controller-operator-history
- **operator_operates_mine:** Arch Of Wyoming LLC → Medicine Bow Mine; 1989-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ashland Inc et al → Arch Of Wyoming LLC; 1989-03-01 to 2006-04-04; source msha-controller-operator-history
- **controller_controls_mine:** Arch Resources Inc → Medicine Bow Mine; 2006-04-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Arch Resources Inc → Arch Of Wyoming LLC; 2006-04-05 to current/open; source msha-controller-operator-history