Russel founded the Watchtower Society (under a slightly different name) and began publication of the
Watchtower, hence why the witnesses claim him. The fact that practically none of his teachings - his pyramidology, his significance for 1799, 1874, etc - are accepted is never talked about, nor the fact that he allowed innocuous things such as birthdays and holidays and using the symbol of the cross.
My impression of Russel is of a rather odd fellow with a strong bent toward mysticism and tangled application of every phrase of every scripture to the most ludicrous things (other people can give some specific examples), who eventually got caught up in believing there was something special to his publishing corporation and his ideas. But he didn't turn it into the controlling organization we know and loathe, just provided some of the basic odd witness doctrine as well as some painfully convoluted literature.
It wasn't until after his death, when Rutherford seized control, that what I consider the more distinctive and dangerous aspects of the current organization appeared: the proscribed refusal of medical procedures like vaccinations and blood transfusions (and organ transplants later); the fanatic efforts to keep "clean" from the world by avoiding pagan or God-dishonoring holidays like Mother's Day, the flag salute, etc; and the tightening of control over the local congregations to a stranglehold. Rutherford also gave them the name Jehovah's Witnesses (Russel had only called his followers Bible Students; there are still groups of Bible Students remaining today.)
Hope this helps, and let me know if you want some more specifics.
-T.