# Relationship history for MSHA mine 2100458

Current hierarchy: **Robertson James A → Arrowhead Sand & Gravel Inc → Arrowhead Sand & Gravel Pit**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** James L  Holmgren et al → Arrowhead Sand & Gravel Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Arrowhead Sand & Gravel Inc → Arrowhead Sand & Gravel Pit; 1950-01-01 to 1980-09-11; source msha-controller-operator-history
- **controller_controls_mine:** Robertson James A → Arrowhead Sand & Gravel Pit; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robertson James A → Arrowhead Sand & Gravel Inc; 1950-01-01 to 1980-09-11; source msha-controller-operator-history
- **operator_operates_mine:** Ken Sons Services → Arrowhead Sand & Gravel Pit; 1980-09-12 to 1981-07-27; source msha-controller-operator-history
- **controller_controls_operator:** James L  Holmgren et al → Ken Sons Services; 1980-09-12 to 1981-07-27; source msha-controller-operator-history
- **controller_controls_operator:** Kenneth  Holmgren et al → Ken Sons Services; 1980-09-12 to 1981-07-27; source msha-controller-operator-history
- **operator_operates_mine:** Arrowhead Sand & Gravel Inc → Arrowhead Sand & Gravel Pit; 1981-07-28 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Robertson James A → Arrowhead Sand & Gravel Inc; 1981-07-28 to current/open; source msha-controller-operator-history