Complex sentence: After WWII he became an X-Ray technician in Puerto Rico and in the 1950's he moved to Montana and joined the Department of Health, Education and Welfare, and was transferred to Washington, DC where he worked as an X-Ray technician until 1957.
Split into simpler sentences: After WWII he became an X-Ray technician in Puerto Rico, until in the 1950's he moved to Montana and joined the Department of Health, Education and Welfare. He was later transferred to Washington, DC where he worked as an X-Ray technician until 1957.