# Relationship history for MSHA mine 2500881

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta Aggregates → #278 Auburn Road Gravel**

- 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

- **controller_controls_mine:** Hopper Chester & Raymond → #278 Auburn Road Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Martin Marietta Materials Inc → #278 Auburn Road Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Nemaha Valley Construction Company → #278 Auburn Road Gravel; 1950-01-01 to 1978-12-25; source msha-controller-operator-history
- **controller_controls_mine:** Nemaha Valley Construction Company → #278 Auburn Road Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Nemaha Valley Construction Company → Nemaha Valley Construction Company; 1950-01-01 to 1978-12-25; source msha-controller-operator-history
- **operator_operates_mine:** Hopper Brothers Quarries → #278 Auburn Road Gravel; 1978-12-26 to 1980-07-31; source msha-controller-operator-history
- **controller_controls_operator:** Hopper Chester & Raymond → Hopper Brothers Quarries; 1978-12-26 to 1980-07-31; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Aggregates → #278 Auburn Road Gravel; 1980-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Aggregates; 1980-08-01 to current/open; source msha-controller-operator-history