# Relationship history for MSHA mine 1900297

Current hierarchy: **Jeffrey A  Douglass → Westport Sand & Gravel Corp → Westport Sand & Gravel Pit & Mill**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **operator_operates_mine:** Westport Sand & Gravel Corp → Westport Sand & Gravel Pit & Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Jeffrey A  Douglass  et al → Westport Sand & Gravel Pit & Mill; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Jeffrey A  Douglass  et al → Westport Sand & Gravel Corp; 1950-01-01 to current/open; source msha-controller-operator-history