It was not until 1920 ( ) American women had the chance to v

强调句式It is not until sometime that。。。对American women didn't have the chance to vote in national elections until 1920。进行强调,要把not until放在一起。这种强调句有一个固定的结构：It is。。。that,它不是时间状语从句。如果去掉not until,变成It was 1920。。。的时候就要用when（It was 1920 when American women had the chance to vote in national elections。）,这个时候就是时间状语从句了