# Relationship history for MSHA mine 4700750

Current hierarchy: **Heidelberg Materials AG → Lehigh Portland Cement Company → Milwaukee Grinding 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: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Heidelberg Materials AG → Milwaukee Grinding Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Universal Atlas Cement Company → Milwaukee Grinding Plant; 1950-01-01 to 1980-10-19; source msha-controller-operator-history
- **controller_controls_mine:** USX Corp (United States Steel Corp) → Milwaukee Grinding Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** USX Corp (United States Steel Corp) → Universal Atlas Cement Company; 1950-01-01 to 1980-10-19; source msha-controller-operator-history
- **operator_operates_mine:** Lehigh Portland Cement Company → Milwaukee Grinding Plant; 1980-10-20 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Heidelberg Materials AG → Lehigh Portland Cement Company; 1980-10-20 to current/open; source msha-controller-operator-history