# Relationship history for MSHA mine 4801192

Current hierarchy: **Chevron Corporation → Pittsburg & Midway Coal Mining Company → North Block 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:** Chevron Corporation → North Block Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Lincoln Corporation → North Block Mine; 1971-08-01 to 1981-09-24; source msha-controller-operator-history
- **operator_operates_mine:** Kemmerer Coal Company → North Block Mine; 1978-11-01 to 1981-09-24; source msha-controller-operator-history
- **controller_controls_operator:** Lincoln Corporation → Kemmerer Coal Company; 1978-11-01 to 1981-09-24; source msha-controller-operator-history
- **operator_operates_mine:** Pittsburg & Midway Coal Mining Company → North Block Mine; 1981-09-25 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Chevron Corporation → Pittsburg & Midway Coal Mining Company; 1981-09-25 to current/open; source msha-controller-operator-history