# Relationship history for MSHA mine 1900338

Current hierarchy: **CRH PLC → Monson Sand & Gravel → Monson Sand & Gravel**

- 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

- **operator_operates_mine:** Monson Sand & Gravel Corp → Monson Sand & Gravel; 1950-01-01 to 2001-01-31; source msha-controller-operator-history
- **controller_controls_mine:** William B  Thornton → Monson Sand & Gravel; 1950-01-01 to 2001-01-31; source msha-controller-operator-history
- **controller_controls_operator:** William B  Thornton → Monson Sand & Gravel Corp; 1950-01-01 to 2001-01-31; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Monson Sand & Gravel; 1994-10-18 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** CRH PLC → Monson Sand & Gravel; 1996-09-09 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Balf Company → Monson Sand & Gravel; 2001-02-01 to 2003-03-09; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Balf Company; 2001-02-01 to 2003-03-09; source msha-controller-operator-history
- **operator_operates_mine:** Monson Sand & Gravel → Monson Sand & Gravel; 2003-03-10 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** CRH PLC → Monson Sand & Gravel; 2003-03-10 to current/open; source msha-controller-operator-history