# Relationship history for MSHA mine 1200995

Current hierarchy: **Continental Concrete Pipe Corp → Continental Sand & Gravel Inc → Continental Sand & Gravel Incorporated**

- 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:** K & K Sand & Gravel Company → Continental Sand & Gravel Incorporated; 1950-01-01 to 1979-04-23; source msha-controller-operator-history
- **controller_controls_mine:** K & K Sand & Gravel Company → Continental Sand & Gravel Incorporated; 1950-01-01 to 1979-04-23; source msha-controller-operator-history
- **controller_controls_operator:** K & K Sand & Gravel Company → K & K Sand & Gravel Company; 1950-01-01 to 1979-04-23; source msha-controller-operator-history
- **operator_operates_mine:** Continental Sand & Gravel Inc → Continental Sand & Gravel Incorporated; 1979-04-24 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Continental Concrete Pipe Corp → Continental Sand & Gravel Incorporated; 1979-04-24 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Continental Concrete Pipe Corp → Continental Sand & Gravel Inc; 1979-04-24 to current/open; source msha-controller-operator-history