# Relationship history for MSHA mine 1300021

Current hierarchy: **Don  Iverson → River City Stone Inc → Browns Bottom Quarry**

- 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

- **operator_operates_mine:** Dubuque Sand & Gravel Company → Browns Bottom Quarry; 1950-01-01 to 1985-03-31; source msha-controller-operator-history
- **controller_controls_mine:** Thompson Floyd → Browns Bottom Quarry; 1950-01-01 to 1985-08-04; source msha-controller-operator-history
- **controller_controls_operator:** Thompson Floyd → Dubuque Sand & Gravel Company; 1950-01-01 to 1985-03-31; source msha-controller-operator-history
- **operator_operates_mine:** River City Stone Inc → Browns Bottom Quarry; 1985-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Don  Iverson et al → Browns Bottom Quarry; 1985-04-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Don  Iverson et al → River City Stone Inc; 1985-04-01 to current/open; source msha-controller-operator-history