# Relationship history for MSHA mine 2101302

Current hierarchy: **James L  Holmgren → Northland Constructors → H.P. 400**

- 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:** James L  Holmgren et al → H.P. 400; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Walter Baker Sand & Gravel → H.P. 400; 1950-01-01 to 1979-06-27; source msha-controller-operator-history
- **controller_controls_mine:** Baker Walter → H.P. 400; 1950-01-01 to 1979-06-27; source msha-controller-operator-history
- **controller_controls_operator:** Baker Walter → Walter Baker Sand & Gravel; 1950-01-01 to 1979-06-27; source msha-controller-operator-history
- **operator_operates_mine:** Ken Sons Services → H.P. 400; 1979-06-28 to 1985-08-05; source msha-controller-operator-history
- **controller_controls_operator:** James L  Holmgren et al → Ken Sons Services; 1979-06-28 to 1985-08-05; source msha-controller-operator-history
- **controller_controls_operator:** Kenneth  Holmgren et al → Ken Sons Services; 1979-06-28 to 1985-08-05; source msha-controller-operator-history
- **operator_operates_mine:** Northland Crushing → H.P. 400; 1985-08-06 to 2014-12-04; source msha-controller-operator-history
- **controller_controls_mine:** James L  Holmgren → H.P. 400; 1985-08-06 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** James L  Holmgren → Northland Crushing; 1985-08-06 to 2014-12-04; source msha-controller-operator-history
- **controller_controls_mine:** James L  Holmgren → H.P. 400; 2014-10-17 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Northland Constructors → H.P. 400; 2014-12-05 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** James L  Holmgren → Northland Constructors; 2014-12-05 to current/open; source msha-controller-operator-history