# Relationship history for MSHA mine 2200121

Current hierarchy: **Patricia  Hughes → American Sand & Gravel Company → Plant U**

- 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

- **operator_operates_mine:** Underwood Sand & Gravel Company → Plant U; 1950-01-01 to 1984-03-02; source msha-controller-operator-history
- **controller_controls_mine:** Underwood Gerald J → Plant U; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Underwood Gerald J → Underwood Sand & Gravel Company; 1950-01-01 to 1984-03-02; source msha-controller-operator-history
- **controller_controls_mine:** Patricia  Hughes  et al → Plant U; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** American Sand & Gravel Company → Plant U; 1984-03-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Patricia  Hughes  et al → American Sand & Gravel Company; 1984-03-03 to current/open; source msha-controller-operator-history