# Relationship history for MSHA mine 4103731

Current hierarchy: **Milam Sam & David Ramirez → Horizon Sand & Gravel Company → Horizon 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

- **operator_operates_mine:** Horizon Sand & Gravel Company → Horizon Sand & Gravel; 1992-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Milam Sam & David Ramirez → Horizon Sand & Gravel; 1992-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Milam Sam & David Ramirez → Horizon Sand & Gravel Company; 1992-06-01 to current/open; source msha-controller-operator-history