So successful was he that he has been called the Father of American Grape Culture. The growing tide of German immigrants coming down the Ohio Valley to Cincinnati liked his wine. Longworth had found a lucrative market: the new German immigrants wanted an affordable, drinkable table wine to continue with the traditions of their homeland, and he enjoyed a virtual monopoly. With his success in wine making, Longworth participated in charitable giving throughout Cincinnati, including a noteworthy donation to the land which the Cincinnati Observatory is built on. Besides being a pioneer and leading horticultural expert in his section, he was recognized as an authority in national horticultural matters. His writings, though individually short and now out of date, exercised a wide influence in his day.