File:Delta-chicagotrib1950ad.png

Summary
Vintage Chicago Tribune advert for Delta air lines, circa 1950. From repository.duke.edu/digitalcollections/adaccess_71273 cited at schoolhouse.georgiahistory.com/wp-content/uploads/2016/02/GHS-Advertising-Poster-for-Classroom-Use-2-4-16.pdf

As this pre-dates the +1-800 InWATS system (as first deployed in 1966-67 by AT&amp;T) the company had to use different local numbers in each community. A large city would have had seven-digit numbers (2L+5N) and Telephone Exchange Names in that era.