No, it is mid to late twentieth century
mid twentieth century.
Black family income increased dramatically.
Yes. The prefix mid- is hyphenated when it is used with numerals or written-out numbers. For example, the mid-twentieth century.
World War II
World War 2.
Peter A. BERTOCCI has written: 'Mid-twentieth century American philosophy'
Polio is a terrible disease that afflicted thousands of young people in the mid twentieth century.
The technology was not available to permit space travel until the mid twentieth century.
The Holocaust.
On the Twentieth Century was created in 1978.
Reconstructionist Judaism. It was in the early to mid twentieth century, not the 1800s.