# Relationship history for MSHA mine 4102936

Current hierarchy: **USX Corp (United States Steel Corp) → Universal Atlas Cement Company → Waco 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:** USX Corp (United States Steel Corp) → Waco Quarry; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Universal Atlas Cement Company → Waco Quarry; 1979-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** USX Corp (United States Steel Corp) → Universal Atlas Cement Company; 1979-10-01 to current/open; source msha-controller-operator-history