# Relationship history for MSHA mine 2300862

Current hierarchy: **Mark T  Simpson; Michael G  Simpson → Simpson Sand & Gravel Company Inc → Simpson Sand And Gravel Pit And 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

- **operator_operates_mine:** Simpson Sand & Gravel Company Inc → Simpson Sand And Gravel Pit And Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Michael G  Simpson et al → Simpson Sand And Gravel Pit And Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Michael G  Simpson et al → Simpson Sand & Gravel Company Inc; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Mark T  Simpson et al → Simpson Sand & Gravel Company Inc; 1950-01-01 to current/open; source msha-controller-operator-history