# Relationship history for MSHA mine 1800072

Current hierarchy: **Boral Limited → Baltimore Brick Company → Rossville 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:** Baltimore Brick Company → Rossville Pit; 1950-01-01 to 1981-07-16; source msha-controller-operator-history
- **controller_controls_mine:** Arundel Corp → Rossville Pit; 1950-01-01 to 1981-07-16; source msha-controller-operator-history
- **controller_controls_operator:** Arundel Corp → Baltimore Brick Company; 1950-01-01 to 1981-07-16; source msha-controller-operator-history
- **operator_operates_mine:** Baltimore Brick Company → Rossville Pit; 1981-07-17 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Boral Limited → Rossville Pit; 1981-07-17 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Boral Limited → Baltimore Brick Company; 1981-07-17 to current/open; source msha-controller-operator-history