George Whitefield, one of the greatest evangelists in church history, was a pioneer in open-air preaching. Rather than having the people come to him, he went where the people were. This itinerant ministry took him throughout England, Scotland, and several times to America.
Here’s what Whitefield had to say in 1741 on his open-air preaching:
Let not the adversaries say I have thrust myself out. No;they have thrust me out. And since the self-righteous men of this generation count themselves unworthy, I go out into the highways and hedges, and compel harlots, publicans and sinners to come in, that my Master’s house may be filled. (quoted in Arnold Dallimore, George Whitefield: God’d Anointed Servant, Kindle loc. 686-689, emphasis mine)