# Relationship history for MSHA mine 3901478

Current hierarchy: **Knife River Corporation → Knife River - South Dakota → Corson Sand Plant / Quarry**

- 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:** Gerald P  Sweetman → Corson Sand Plant / Quarry; 1950-01-01 to 2018-10-03; source msha-controller-operator-history
- **operator_operates_mine:** Knife River - South Dakota → Corson Sand Plant / Quarry; 2003-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Gerald P  Sweetman → Knife River - South Dakota; 2003-04-01 to 2018-10-03; source msha-controller-operator-history
- **controller_controls_mine:** MDU Resources Group Inc → Corson Sand Plant / Quarry; 2018-10-04 to 2023-05-31; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → Knife River - South Dakota; 2018-10-04 to 2023-05-31; source msha-controller-operator-history
- **controller_controls_mine:** Knife River Corporation → Corson Sand Plant / Quarry; 2023-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Knife River Corporation → Knife River - South Dakota; 2023-06-01 to current/open; source msha-controller-operator-history