# Relationship history for MSHA mine 3605205

Current hierarchy: **Frank Bryan Inc → Georgetown Sand & Gravel, Inc. → Georgetown Sand & Gravel Inc.**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Martin Marietta Materials Inc → Georgetown Sand & Gravel Inc.; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Dravo Basic Materials Company Inc → Georgetown Sand & Gravel Inc.; 1950-01-01 to 1995-01-02; source msha-controller-operator-history
- **controller_controls_mine:** Dravo Corp → Georgetown Sand & Gravel Inc.; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Dravo Corp → Dravo Basic Materials Company Inc; 1950-01-01 to 1995-01-02; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Aggregates → Georgetown Sand & Gravel Inc.; 1995-01-03 to 1996-07-15; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Aggregates; 1995-01-03 to 1996-07-15; source msha-controller-operator-history
- **operator_operates_mine:** Georgetown Sand & Gravel, Inc. → Georgetown Sand & Gravel Inc.; 1996-07-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Frank Bryan Inc → Georgetown Sand & Gravel Inc.; 1996-07-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Frank Bryan Inc → Georgetown Sand & Gravel, Inc.; 1996-07-16 to current/open; source msha-controller-operator-history