# Relationship history for MSHA mine 2900845

Current hierarchy: **Chevron Corporation → Pittsburg & Midway Coal Mining Company → York Canyon Surface 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 → York Canyon Surface Mine; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Kaiser Coal Corp Of York Canyon → York Canyon Surface Mine; 1972-10-01 to 1989-02-10; source msha-controller-operator-history
- **controller_controls_mine:** Kaiser Steel Corp → York Canyon Surface Mine; 1972-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kaiser Steel Corp → Kaiser Coal Corp Of York Canyon; 1972-10-01 to 1989-02-10; source msha-controller-operator-history
- **operator_operates_mine:** Pittsburg & Midway Coal Mining Company → York Canyon Surface Mine; 1989-02-11 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Chevron Corporation → Pittsburg & Midway Coal Mining Company; 1989-02-11 to current/open; source msha-controller-operator-history