# Relationship history for MSHA mine 2100875

Current hierarchy: **Bolles Glenn → Anchor Block & Concrete Company → Maple Grove Pit**

- 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:** Shakopee Sand & Gravel Company → Maple Grove Pit; 1950-01-01 to 1982-12-06; source msha-controller-operator-history
- **controller_controls_mine:** Roberts Harold → Maple Grove Pit; 1950-01-01 to 1982-12-06; source msha-controller-operator-history
- **controller_controls_operator:** Roberts Harold → Shakopee Sand & Gravel Company; 1950-01-01 to 1982-12-06; source msha-controller-operator-history
- **operator_operates_mine:** Anchor Block & Concrete Company → Maple Grove Pit; 1982-12-07 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Bolles Glenn → Maple Grove Pit; 1982-12-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Bolles Glenn → Anchor Block & Concrete Company; 1982-12-07 to current/open; source msha-controller-operator-history