# Relationship history for MSHA mine 2500902

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta-Construction Aggregates Division → Du Bois Quarry**

- 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

- **controller_controls_mine:** Hopper Chester & Raymond → Du Bois Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → Du Bois Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hopper Brothers Quarries → Du Bois Quarry; 1978-03-09 to 1980-08-07; source msha-controller-operator-history
- **controller_controls_operator:** Hopper Chester & Raymond → Hopper Brothers Quarries; 1978-03-09 to 1980-08-07; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta-Construction Aggregates Division → Du Bois Quarry; 1980-08-08 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta-Construction Aggregates Division; 1980-08-08 to current/open; source msha-controller-operator-history