Of the 30 on the Dow in 1955 the survivors are:
duPont
General Electric
Proctor & Gamble
Chevron (was called Standard Oil of California) which was off the Dow for a while and is now back on.
Exxon Mobil (was called Standard Oil of New Jersey)
United Technologies (was called United Aircraft Company)
Info from https://en.wikipedia.org/wiki/Historical_components_of_the_Dow_Jones_Industrial_Average
~ 20%.
Someone should examine 23,000 vs inflation and whatever lame methodology used to make the replacements along the way.
Thanks for your post!