P.B. Chamberlain was the founder and first pastor of First Congregational Church of Walla Walla. Founded in 1864, it is the oldest Congregational church in Washington. 

Chamberlain first arrived in Walla Walla in 1862, having been dismissed as pastor of First Congregational Church in Portland, Oregon Territory. Having assumed the Portland position in 1855, his first pastorate out of theological seminary in Maine, he managed to grow the congregation rapidly. However, his bombastic rhetoric, virulent anti-secret society, anti-Roman Catholic, anti-women's suffrage, and unchecked tendency to pass judgment on others' lifestyles soon began to drain away his congregation to the point where the church was no longer able to meet his salary. 

He was a larger than life character, and a fairly important man in Walla Walla's history, though he is not nearly so remembered today as many other local pioneers. He attracted large crowds to his lectures, but due to his bombast, he was never able to  grow his church here despite preaching until retiring in 1879. He died in Walla Walla and his entire family is buried at Mountain View Cemetery.

P.B. Chamberlain is portrayed by Steve Wilen.