# Relationship history for MSHA mine 0800189

Current hierarchy: **Williams J M → U S Agri-Chemicals Corp → Rockland Mine**

- 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

- **operator_operates_mine:** Uss Agri-Chemical Division → Rockland Mine; 1950-01-01 to 1989-02-28; source msha-controller-operator-history
- **controller_controls_mine:** USX Corp (United States Steel Corp) → Rockland Mine; 1950-01-01 to 1989-02-28; source msha-controller-operator-history
- **controller_controls_operator:** USX Corp (United States Steel Corp) → Uss Agri-Chemical Division; 1950-01-01 to 1989-02-28; source msha-controller-operator-history
- **operator_operates_mine:** U S Agri-Chemicals Corp → Rockland Mine; 1989-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Williams J M → Rockland Mine; 1989-03-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Williams J M → U S Agri-Chemicals Corp; 1989-03-01 to current/open; source msha-controller-operator-history