# Relationship history for MSHA mine 3901428

Current hierarchy: **Sanborn County-Sd → Sanborn County Highway → PORTABLE NO 1**

- 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:** Sanborn County-Sd → PORTABLE NO 1; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Sanborn County Highway → PORTABLE NO 1; 1998-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Sanborn County-Sd → Sanborn County Highway; 1998-07-01 to current/open; source msha-controller-operator-history