# Relationship history for MSHA mine 4400136

Current hierarchy: **Vulcan Materials Company → Vulcan Construction Materials, LLC → Skippers**

- 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:** Legacy Vulcan Corp (Form:Vulcan Materials Co) → Skippers; 1950-01-01 to 2007-11-15; source msha-controller-operator-history
- **operator_operates_mine:** Trego Stone Corp → Skippers; 1950-01-01 to 1991-08-21; source msha-controller-operator-history
- **controller_controls_mine:** Boxley Materials Co → Skippers; 1950-01-01 to 1991-08-21; source msha-controller-operator-history
- **controller_controls_operator:** Boxley Materials Co → Trego Stone Corp; 1950-01-01 to 1991-08-21; source msha-controller-operator-history
- **operator_operates_mine:** Vulcan Construction Materials, LLC → Skippers; 1991-08-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Legacy Vulcan Corp (Form:Vulcan Materials Co) → Vulcan Construction Materials, LLC; 1991-08-22 to 2007-11-15; source msha-controller-operator-history
- **controller_controls_mine:** Vulcan Materials Company → Skippers; 2007-11-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Vulcan Materials Company → Vulcan Construction Materials, LLC; 2007-11-16 to current/open; source msha-controller-operator-history