On 2022-07-11, “Thor—From Cold War Stopgap Weapon to Workhorse Satellite Launcher” discussed the origin of the Thor intermediate range ballistic missile (IRBM) as a stop-gap developed (in just three years from inception to military deployment) in case the more complex and technologically risky Atlas ICBM did not work.
After the Atlas became operational, Thor missiles were retired by 1963, with both the U.S. Air Force and NASA repurposing the weapons as the first stage of satellite launchers, evolving into the Delta series, the last of which, Delta IV Heavy, remains active today.
This video discusses the first steps from Thor to Delta.