Here's an example of a US phone book from the 1980s, https://archive.org/details/1981-12-mc-lean-county-phone-book/mode/2up https://archive.org/details/1981-12-

Here's an example of a US phone book from the 1980s, https://archive.org/details/1981-12-mc-lean-county-phone-book/mode/2up https://archive.org/details/1981-12-mc-lean-county-phone-boo... . It has two sections, typically called 'white pages' and 'yellow pages' because the paper for the latter was tinted yellow. The white pages had subscriber phone numbers, listed alphabetically, with no advertising except that one could pay extra to have the entry in bold, to grab attention. The yellow pages were for business numbers, arranged by topic. A business could buy ad space to put on the same page as the topic. In the linked-to example, the white and yellow pages were in the same book. In a more populated area, the two would be separate books, and in larger cities even two books for the white pages and one for the yellow.