# Relationship history for MSHA mine 2301915

Current hierarchy: **CRH PLC → Hilty Quarries Inc → Portable Plant #1**

- 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

- **controller_controls_mine:** John  Hilty  et al → Portable Plant #1; 1950-01-01 to 2009-11-03; source msha-controller-operator-history
- **operator_operates_mine:** Hilty Quarries Inc → Portable Plant #1; 1985-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** John  Hilty  et al → Hilty Quarries Inc; 1985-05-01 to 2009-11-03; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Portable Plant #1; 2009-11-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Hilty Quarries Inc; 2009-11-04 to current/open; source msha-controller-operator-history