Yes Virginia, once upon a time, all grapes had seeds.
These seeded grapes were used primarily for making raisins, but their seeds needed to be removed. One could always pop the seed out of the skin but that proved labor intensive and very costly. The most common practice was to plump the grapes up with heated water so as to make it easy to deseed the grape. This created a sticky problem though, because the sugars from the grapes rose to the surface creating sticky raisins.
In 1872, it all changed though.
A Scottish immigrant turned California vineyard owner, William Thompson, imported a variety of grape from areas of modern Iran or Turkey. Working with local rootstock, in 1876 he was able to create a 50 pound crop of thin-skinned, sweet, seedless grapes. He shared several cuttings with friends, including J.P. Onstott. From those cuttings, more cuttings were shared and by 1920 the Thompson seedless grape was the preferred raisin variety grape. This was the first commercialized seedless grape.
After the popularity of the seedless white grape, seedless reds were developed, and later black seedless too. Today the seedless grape varieties have overtaken the popularity of the seeded grapes.
By the way, the Thompson seedless grapes, aren’t really ‘seedless’ – they have small undeveloped seeds that go unnoticed.