# Relationship history for MSHA mine 4000742

Current hierarchy: **Martin Marietta Materials Inc → Martin Marietta Aggregates → Sewanee Plant**

- 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:** Martin Marietta Materials Inc → Sewanee Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Wedron Silica Division → Sewanee Plant; 1950-01-01 to 1979-04-30; source msha-controller-operator-history
- **controller_controls_mine:** Sherman County - KS → Sewanee Plant; 1950-01-01 to 1979-04-30; source msha-controller-operator-history
- **controller_controls_operator:** Sherman County - KS → Wedron Silica Division; 1950-01-01 to 1979-04-30; source msha-controller-operator-history
- **operator_operates_mine:** Wedron Silica Company → Sewanee Plant; 1979-05-01 to 1979-09-11; source msha-controller-operator-history
- **controller_controls_mine:** Twentieth Century Fox → Sewanee Plant; 1979-05-01 to 1979-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Twentieth Century Fox → Wedron Silica Company; 1979-05-01 to 1979-09-11; source msha-controller-operator-history
- **operator_operates_mine:** Martin Marietta Aggregates → Sewanee Plant; 1979-09-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Martin Marietta Materials Inc → Martin Marietta Aggregates; 1979-09-12 to current/open; source msha-controller-operator-history