Like most online services, the system for searching and tracking down a telephone numbers owners started out as analog searches. Printed reverse phone directories have been produced by telephone companies for decades before the conception of computers and the internet.
These reverse phone directories were distributed to phone companies, law enforcement, libraries and private businesses that required them.
In the early nineties, there were private businesses that offered a reverse telephone lookups for small fees, but they started building larger and larger databases that included much more information than just the names and addresses of the phone number owners.
Then with the dawn of the internet and its availability to the general public, the online reverse lookup directories were made available, and now include information on cellular phone owners. There are still free reverse phone services at most countries, in the US for example, there are public 411 and reverse number directories, and there are similar services in other countries.
However, these free reverse phone directories do not provide information on cellular phone numbers, there have been great concerns on including cell phone numbers into free public 411s and reverse number directories. There are organizations that have opposed the inclusion and presently in most countries, cellular phone numbers are not available in public reverse phone directories.
This is easily remedied though by private reverse phone directories that offer searches for cellular phone owners. These companies, collect their data from various sources, both paid and public, and in turn charge a small fee for their services.
Online reverse phone lookup service also go beyond just providing names and addresses, they now provide court records, criminal records, as well as other public records, which anyone can access through online reverse phone directory sites.