# Relationship history for MSHA mine 4502166

Current hierarchy: **Heidelberg Materials AG → HM Northwest Cement Company → Lehigh Northwest Cement Company**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **operator_operates_mine:** Columbia Northwest Corp → Lehigh Northwest Cement Company; 1950-01-01 to 1985-08-28; source msha-controller-operator-history
- **controller_controls_mine:** Ashland Inc → Lehigh Northwest Cement Company; 1950-01-01 to 1985-08-28; source msha-controller-operator-history
- **controller_controls_operator:** Ashland Inc → Columbia Northwest Corp; 1950-01-01 to 1985-08-28; source msha-controller-operator-history
- **operator_operates_mine:** Columbia Northwest Corp → Lehigh Northwest Cement Company; 1985-08-29 to 1987-09-23; source msha-controller-operator-history
- **controller_controls_mine:** Michael  Carlow  et al → Lehigh Northwest Cement Company; 1985-08-29 to 1993-08-01; source msha-controller-operator-history
- **controller_controls_operator:** Michael  Carlow  et al → Columbia Northwest Corp; 1985-08-29 to 1987-09-23; source msha-controller-operator-history
- **operator_operates_mine:** Tilbury Cement Company → Lehigh Northwest Cement Company; 1987-09-24 to 2000-07-20; source msha-controller-operator-history
- **controller_controls_mine:** Cimenteries Cbr Cementbedrijven → Lehigh Northwest Cement Company; 1987-09-24 to 2000-07-20; source msha-controller-operator-history
- **controller_controls_operator:** Cimenteries Cbr Cementbedrijven → Tilbury Cement Company; 1987-09-24 to 2000-07-20; source msha-controller-operator-history
- **operator_operates_mine:** Lehigh Cement Co → Lehigh Northwest Cement Company; 2000-07-21 to 2008-01-02; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Lehigh Northwest Cement Company; 2000-07-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Lehigh Cement Co; 2000-07-21 to 2008-01-02; source msha-controller-operator-history
- **operator_operates_mine:** HM Northwest Cement Company → Lehigh Northwest Cement Company; 2008-01-03 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Heidelberg Materials AG → Lehigh Northwest Cement Company; 2008-01-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → HM Northwest Cement Company; 2008-01-03 to current/open; source msha-controller-operator-history