# Relationship history for MSHA mine 3900087

Current hierarchy: **Aurora County-SD → Aurora County Highway Department → AURORA**

- 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:** Aurora County-SD → AURORA; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Aurora County Highway Department → AURORA; 1993-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Aurora County-SD → Aurora County Highway Department; 1993-05-01 to current/open; source msha-controller-operator-history