There has been tons of sound change over the last 100 years. In old radio broadcasts you hear lots of sounds you don't hear any more, especially in regional dialects that have either changed or been levelled out of existence. Check out this spellbinding speech from Calvin Coolidge in 1924: https://www.youtube.com/watch?v=xfF-xv7rc20
We've got...
* Non-rhotic dialect with "earnings" as [əjnɪŋz]
* Final /ɪ/ as in British English, not /i/ as in modern American English. "Country" is [k@ntrɪ].
* /p/ is clearly unaspirated
* "paid" is [pɛ:d], not [peɪd] as in modern American English
* "grant" is [grɑnt] not [grænt]
As another example, the Northern Cities vowel shift (for example "Chicago" pronounced [ʃɪkægo]) only really got going in the 1960s.