# Relationship history for MSHA mine 2400015

Current hierarchy: **CRH PLC → Ash Grove Cement Company → MONTANA CITY PLANT**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** Ash Grove Cement Company → MONTANA CITY PLANT; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **operator_operates_mine:** Kaiser Cement Corp → MONTANA CITY PLANT; 1950-01-01 to 1987-04-15; source msha-controller-operator-history
- **controller_controls_mine:** Kaiser Cement Corp → MONTANA CITY PLANT; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Kaiser Cement Corp → Kaiser Cement Corp; 1950-01-01 to 1987-04-15; source msha-controller-operator-history
- **operator_operates_mine:** Ash Grove Cement Company → MONTANA CITY PLANT; 1987-04-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Ash Grove Cement Company; 1987-04-16 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → MONTANA CITY PLANT; 2018-06-21 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Ash Grove Cement Company; 2018-06-21 to current/open; source msha-controller-operator-history