# Relationship history for MSHA mine 1503783

Current hierarchy: **United  Company → Wellmore Coal Corp → Wellmore #17 So Elkhorn 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: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** United  Company → Wellmore #17 So Elkhorn Plant; 1950-01-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Kentucky Elkhorn Coal Company → Wellmore #17 So Elkhorn Plant; 1950-01-01 to 1977-07-10; source msha-controller-operator-history
- **controller_controls_mine:** Johnson Donald T → Wellmore #17 So Elkhorn Plant; 1950-01-01 to 1977-07-10; source msha-controller-operator-history
- **controller_controls_operator:** Johnson Donald T → Kentucky Elkhorn Coal Company; 1950-01-01 to 1977-07-10; source msha-controller-operator-history
- **operator_operates_mine:** Southern Elkhorn Coal Corp → Wellmore #17 So Elkhorn Plant; 1977-07-11 to 1981-09-30; source msha-controller-operator-history
- **controller_controls_mine:** International Minerals & Chemical Corp → Wellmore #17 So Elkhorn Plant; 1977-07-11 to 1983-04-02; source msha-controller-operator-history
- **controller_controls_operator:** International Minerals & Chemical Corp → Southern Elkhorn Coal Corp; 1977-07-11 to 1981-09-30; source msha-controller-operator-history
- **operator_operates_mine:** Wellmore Coal Corp → Wellmore #17 So Elkhorn Plant; 1981-10-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** United  Company → Wellmore Coal Corp; 1981-10-01 to current/open; source msha-controller-operator-history