# Relationship history for MSHA mine 1800572

Current hierarchy: **Vulcan Materials Company → Vulcan Construction Materials, LP → Leonardtown Sand & Gravel**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** Legacy Vulcan Corp (Form:Vulcan Materials Co) → Leonardtown Sand & Gravel; 1950-01-01 to 2007-11-15; source msha-controller-operator-history
- **controller_controls_mine:** Florida Rock Industries Inc → Leonardtown Sand & Gravel; 1950-01-01 to 2007-11-15; source msha-controller-operator-history
- **operator_operates_mine:** C J Langenfelder & Son Inc → Leonardtown Sand & Gravel; 1950-01-01 to 1982-12-19; source msha-controller-operator-history
- **controller_controls_mine:** C J Langenfelder & Son Inc → Leonardtown Sand & Gravel; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** C J Langenfelder & Son Inc → C J Langenfelder & Son Inc; 1950-01-01 to 1982-12-19; source msha-controller-operator-history
- **operator_operates_mine:** Florida Rock Industries Inc → Leonardtown Sand & Gravel; 1982-12-20 to 2007-11-15; source msha-controller-operator-history
- **controller_controls_operator:** Florida Rock Industries Inc → Florida Rock Industries Inc; 1982-12-20 to 2007-11-15; source msha-controller-operator-history
- **controller_controls_mine:** Vulcan Materials Company → Leonardtown Sand & Gravel; 2007-11-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Vulcan Materials Company → Florida Rock Industries Inc; 2007-11-16 to 2007-11-15; source msha-controller-operator-history
- **operator_operates_mine:** Vulcan Construction Materials, LP → Leonardtown Sand & Gravel; 2007-11-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Vulcan Materials Company → Vulcan Construction Materials, LP; 2007-11-16 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Legacy Vulcan Corp (Form:Vulcan Materials Co) → Vulcan Construction Materials, LP; 2007-11-16 to 2007-11-15; source msha-controller-operator-history