# Relationship history for MSHA mine 3200956

Current hierarchy: **Towner County-ND → Towner County Highway Department → Portable**

- 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:** Towner County Highway Department → Portable; 2012-05-08 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Towner County-ND → Portable; 2012-05-08 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Towner County-ND → Towner County Highway Department; 2012-05-08 to current/open; source msha-controller-operator-history