# Relationship history for MSHA mine 2402047

Current hierarchy: **Knife River Corporation → Knife River Billings → Portable #4**

- 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:** Meredith  Reiter → Portable #4; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Empire Sand & Gravel Company Inc → Portable #4; 1994-04-01 to 2000-06-05; source msha-controller-operator-history
- **controller_controls_operator:** Meredith  Reiter → Empire Sand & Gravel Company Inc; 1994-04-01 to 2000-06-05; source msha-controller-operator-history
- **controller_controls_mine:** MDU Resources Group Inc → Portable #4; 1999-09-01 to 2023-05-31; source msha-controller-operator-history
- **operator_operates_mine:** Knife River Billings → Portable #4; 2000-06-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → Knife River Billings; 2000-06-06 to 2023-05-31; source msha-controller-operator-history
- **controller_controls_mine:** Knife River Corporation → Portable #4; 2023-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Knife River Corporation → Knife River Billings; 2023-06-01 to current/open; source msha-controller-operator-history