# Relationship history for MSHA mine 1102836

Current hierarchy: **Prairie Group → Prairie Material Sales, Inc.-Aggregate Division → Yard 97-Pontiac**

- 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:** Albert E  Markgraf → Yard 97-Pontiac; 1979-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Prairie Group → Yard 97-Pontiac; 1984-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Markgraf Materials Company → Yard 97-Pontiac; 1985-09-01 to 1997-09-23; source msha-controller-operator-history
- **controller_controls_operator:** Albert E  Markgraf → Markgraf Materials Company; 1985-09-01 to 1997-09-23; source msha-controller-operator-history
- **operator_operates_mine:** Prairie Material Sales, Inc.-Aggregate Division → Yard 97-Pontiac; 1997-09-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Prairie Group → Prairie Material Sales, Inc.-Aggregate Division; 1997-09-24 to current/open; source msha-controller-operator-history