# Relationship history for MSHA mine 0202237

Current hierarchy: **Peter Kiewit Sons' Inc → Union Rock & Materials Corp → Union Rock & Materials Corp Tonto Creek**

- 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:** Peter Kiewit Sons' Inc → Union Rock & Materials Corp Tonto Creek; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Salt River Pima-Maricopa Indian Community → Union Rock & Materials Corp Tonto Creek; 1981-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Hills Denver L → Union Rock & Materials Corp Tonto Creek; 1983-04-01 to 1988-02-29; source msha-controller-operator-history
- **operator_operates_mine:** Baseline Materials & Custom Crushing → Union Rock & Materials Corp Tonto Creek; 1985-01-01 to 1988-02-29; source msha-controller-operator-history
- **controller_controls_operator:** Hills Denver L → Baseline Materials & Custom Crushing; 1985-01-01 to 1988-02-29; source msha-controller-operator-history
- **operator_operates_mine:** Salt River Sand & Rock → Union Rock & Materials Corp Tonto Creek; 1988-03-01 to 1989-02-26; source msha-controller-operator-history
- **controller_controls_operator:** Salt River Pima-Maricopa Indian Community → Salt River Sand & Rock; 1988-03-01 to 1989-02-26; source msha-controller-operator-history
- **operator_operates_mine:** Union Rock & Materials Corp → Union Rock & Materials Corp Tonto Creek; 1989-02-27 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Peter Kiewit Sons' Inc → Union Rock & Materials Corp; 1989-02-27 to current/open; source msha-controller-operator-history