# Relationship history for MSHA mine 3503321

Current hierarchy: **Knife River Corporation → Knife River Corporation-Northwest → WILLAMETTE PORTABLE #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:** M O  Salmon Sr → WILLAMETTE PORTABLE #1; 1987-07-01 to 1994-11-13; source msha-controller-operator-history
- **operator_operates_mine:** S2-F Corp → WILLAMETTE PORTABLE #1; 1988-10-01 to 1994-11-13; source msha-controller-operator-history
- **controller_controls_operator:** M O  Salmon Sr → S2-F Corp; 1988-10-01 to 1994-11-13; source msha-controller-operator-history
- **operator_operates_mine:** S2-F Corp → WILLAMETTE PORTABLE #1; 1994-11-14 to 1999-12-31; source msha-controller-operator-history
- **controller_controls_mine:** R Gary  Ferguson → WILLAMETTE PORTABLE #1; 1994-11-14 to 1999-12-31; source msha-controller-operator-history
- **controller_controls_operator:** R Gary  Ferguson → S2-F Corp; 1994-11-14 to 1999-12-31; source msha-controller-operator-history
- **controller_controls_mine:** MDU Resources Group Inc → WILLAMETTE PORTABLE #1; 1998-03-05 to 2023-05-31; source msha-controller-operator-history
- **operator_operates_mine:** Knife River Corporation-Northwest → WILLAMETTE PORTABLE #1; 2000-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → Knife River Corporation-Northwest; 2000-01-01 to 2023-05-31; source msha-controller-operator-history
- **controller_controls_mine:** Knife River Corporation → WILLAMETTE PORTABLE #1; 2023-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Knife River Corporation → Knife River Corporation-Northwest; 2023-06-01 to current/open; source msha-controller-operator-history