# Relationship history for MSHA mine 4800987

Current hierarchy: **BHB Limited Partnership; A&M Products → Black Hills Bentonite-A Limited Liability Co → WORLAND PLANT**

- 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

- **operator_operates_mine:** Kaycee Bentonite Corp → WORLAND PLANT; 1950-01-01 to 1987-01-06; source msha-controller-operator-history
- **controller_controls_mine:** T A  Thorson → WORLAND PLANT; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** T A  Thorson → Kaycee Bentonite Corp; 1950-01-01 to 1987-01-06; source msha-controller-operator-history
- **controller_controls_mine:** Thomas A  Thorson et al → WORLAND PLANT; 1987-01-01 to 2020-06-30; source msha-controller-operator-history
- **operator_operates_mine:** Black Hills Bentonite-A Limited Liability Co → WORLAND PLANT; 1987-01-07 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Thomas A  Thorson et al → Black Hills Bentonite-A Limited Liability Co; 1987-01-07 to 2020-06-30; source msha-controller-operator-history
- **controller_controls_mine:** A&M Products et al → WORLAND PLANT; 2020-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** A&M Products et al → Black Hills Bentonite-A Limited Liability Co; 2020-07-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** BHB Limited Partnership et al → Black Hills Bentonite-A Limited Liability Co; 2020-07-01 to current/open; source msha-controller-operator-history