# Relationship history for MSHA mine 2500500

Current hierarchy: **Ronald D  Willers; Marilyn M  Willers → Pilger Sand & Gravel Inc → NORFOLK PLANT**

- 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:** Don  Kellogg → NORFOLK PLANT; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Elkhorn Construction Company → NORFOLK PLANT; 1950-01-01 to 1979-10-31; source msha-controller-operator-history
- **controller_controls_mine:** Elkhorn Construction Company → NORFOLK PLANT; 1950-01-01 to 1979-10-31; source msha-controller-operator-history
- **controller_controls_operator:** Elkhorn Construction Company → Elkhorn Construction Company; 1950-01-01 to 1979-10-31; source msha-controller-operator-history
- **operator_operates_mine:** Mid-West Bridge & Construction Company → NORFOLK PLANT; 1979-11-01 to 1985-06-27; source msha-controller-operator-history
- **controller_controls_operator:** Don  Kellogg → Mid-West Bridge & Construction Company; 1979-11-01 to 1985-06-27; source msha-controller-operator-history
- **controller_controls_mine:** Ronald D  Willers et al → NORFOLK PLANT; 1983-09-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** James H Jansen → NORFOLK PLANT; 1985-06-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Northeast Sand & Gravel Inc → NORFOLK PLANT; 1985-06-28 to 1991-08-18; source msha-controller-operator-history
- **controller_controls_operator:** James H Jansen → Northeast Sand & Gravel Inc; 1985-06-28 to 1991-08-18; source msha-controller-operator-history
- **operator_operates_mine:** Pilger Sand & Gravel Inc → NORFOLK PLANT; 1991-08-19 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ronald D  Willers et al → Pilger Sand & Gravel Inc; 1991-08-19 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Marilyn M  Willers et al → Pilger Sand & Gravel Inc; 1991-08-19 to current/open; source msha-controller-operator-history