# Relationship history for MSHA mine 3503475

Current hierarchy: **Taiheiyo Cement Corp → CalPortland Company → Linnton DBA CalPortland**

- 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:** Taiheiyo Cement Corp → Linnton DBA CalPortland; 1988-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Linnton DBA CalPortland; 1990-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Marilyn  Webb  et al → Linnton DBA CalPortland; 1996-01-01 to 2000-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Columbia River Sand & Gravel Inc → Linnton DBA CalPortland; 1999-03-01 to 2000-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Marilyn  Webb  et al → Columbia River Sand & Gravel Inc; 1999-03-01 to 2000-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Columbia River Sand & Gravel → Linnton DBA CalPortland; 2000-11-01 to 2002-05-15; source msha-controller-operator-history
- **controller_controls_mine:** Taiheiyo Cement Corp → Linnton DBA CalPortland; 2000-11-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Columbia River Sand & Gravel; 2000-11-01 to 2002-05-15; source msha-controller-operator-history
- **operator_operates_mine:** Glacier Northwest Inc. → Linnton DBA CalPortland; 2002-05-16 to 2009-01-12; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → Glacier Northwest Inc.; 2002-05-16 to 2009-01-12; source msha-controller-operator-history
- **operator_operates_mine:** CalPortland Company → Linnton DBA CalPortland; 2009-01-13 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Taiheiyo Cement Corp → CalPortland Company; 2009-01-13 to current/open; source msha-controller-operator-history