In 1750 Benjamin Franklin published a proposal for an experiment to prove that lightning is electricity by flying a kite in a storm that appeared capable of becoming a lightning storm. On May 10, 1752, Thomas Francois d'Alibard of France conducted Franklin's experiment (using a 40-foot-tall iron rod instead of a kite) and extracted electrical sparks from a cloud. On June 15, Franklin conducted his famous kite experiment and also successfully extracted sparks from a cloud, unaware that d'Alibard had already done so, 36 days earlier. Others, such as Prof. Georg Wilhelm Richmann of St. Petersburg, Russia, were spectacularly electrocuted during the months following Franklin's experiment.
Franklin, in his writings, displays that he was aware of the dangers and offered alternative ways to demonstrate that lightning was electrical, as shown by his invention of the lightning rod, an application of the use of electrical ground. If Franklin did perform this experiment, he did not do it in the way that is often described, as it would have been dramatic but fatal. Instead he used the kite to collect some electric charge from a storm cloud, which implied that lightning was electrical.
Painting by Benjamin West, "Franklin Drawing Electricity From A Cloud."