# Relationship history for MSHA mine 4201665

Current hierarchy: **CRH PLC → Ash Grove Cement Company → Leamington Cement 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: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** Ash Grove Cement Company → Leamington Cement Plant; 1950-01-01 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → Leamington Cement Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Southdown Inc → Leamington Cement Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Cement → Leamington Cement Plant; 1980-03-01 to 1984-04-22; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Cement; 1980-03-01 to 1984-04-22; source msha-controller-operator-history
- **operator_operates_mine:** Southwestern Portland Cement Company → Leamington Cement Plant; 1984-04-23 to 1989-05-07; source msha-controller-operator-history
- **controller_controls_operator:** Southdown Inc → Southwestern Portland Cement Company; 1984-04-23 to 1989-05-07; source msha-controller-operator-history
- **operator_operates_mine:** Ash Grove Cement Company → Leamington Cement Plant; 1989-05-08 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ash Grove Cement Company → Ash Grove Cement Company; 1989-05-08 to 2018-06-20; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Leamington Cement 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