History of Toll Free Numbers
1-800 numbers were developed in the late 60s by AT&T as a convenient way for businesses to pay the tolls for their customers who contacted them. As the service became more popular, toll free subscribers began finding new and innovative uses for the service. As usages and popularity began to grow companies began to realize that consumers preferred to do business with companies with 800 numbers.
By 1984, when the Bell System was dismantled by the Justice Department, there were over 3 million 800 numbers in service by AT&T, and new long distance carriers were clamoring to provide 800 service. These carriers were assigned blocks of 800 numbers with common NXX (prefixes), so the phone numbers available depended on the carrier you spoke to and if you left your carrier, you would have to change your 800 number. The numbers weren't portable.
One of the steps in creating a more competitive toll free market, was to implement the current SMS/800 system which allowed true portability of 800 numbers so you could change phone companies without having to change your number. This gave toll free number subscribers much more ownership rights and made the popularity and value of good 800 numbers sky rocket, so much so that within 18 months of the introduction of number portability, very few of the 7 million 800 numbers were left for new subscribers.
Then after rationing 800 numbers, the telecommunications industry chose 888 as the next toll free area code, introducing another 8 million new numbers to the toll free pool. 888 numbers have been in use now for several years and are fairly well accepted and understood by a large part of the country as equivalent to 800 numbers. But as 888 numbers began to dwindle, 877 and later 866 area codes were introduced as well. 855, 844, 833 and 822 are also reserved for toll free use as they are required.