# Relationship history for MSHA mine 2500271

Current hierarchy: **Roland W  Johnson → Johnson Sand & Gravel Corp → Johnson Sand & Gravel**

- 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:** L & L Livestock Inc → Johnson Sand & Gravel; 1950-01-01 to 1981-06-02; source msha-controller-operator-history
- **controller_controls_mine:** L & L Livestock Inc → Johnson Sand & Gravel; 1950-01-01 to 1981-06-02; source msha-controller-operator-history
- **controller_controls_operator:** L & L Livestock Inc → L & L Livestock Inc; 1950-01-01 to 1981-06-02; source msha-controller-operator-history
- **operator_operates_mine:** Loup Gravel Company → Johnson Sand & Gravel; 1981-06-03 to 1983-09-15; source msha-controller-operator-history
- **controller_controls_mine:** Hoffmeister Frank → Johnson Sand & Gravel; 1981-06-03 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Hoffmeister Frank → Loup Gravel Company; 1981-06-03 to 1983-09-15; source msha-controller-operator-history
- **operator_operates_mine:** Johnson Sand & Gravel Corp → Johnson Sand & Gravel; 1983-09-16 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Roland W  Johnson → Johnson Sand & Gravel; 1983-09-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Roland W  Johnson → Johnson Sand & Gravel Corp; 1983-09-16 to current/open; source msha-controller-operator-history