The revival that began on Azusa Street in April 1906 is the origin point of a movement now counted in the hundreds of millions. Its most remarkable feature at the time was not the tongues. It was who was in the room.
Seymour in the hallway
William J. Seymour was the son of former slaves, blind in one eye from smallpox, and had learned the doctrine that speaking in tongues is the evidence of Spirit baptism from Charles Parham in Houston, where segregation law meant Seymour was not permitted to sit in the classroom and listened to the lectures from the hallway.
He carried that doctrine to Los Angeles, was locked out of the church that had invited him for preaching it, and began meeting in a house on Bonnie Brae Street. When the crowds outgrew it the group took a disused building on Azusa Street that had been an African Methodist Episcopal church and latterly a stable and warehouse, and from April 1906 held services more or less continuously for three years.
What was unusual
The meetings were racially mixed, in the United States, in 1906. Black, white, Latino and Asian participants worshipped together, and women preached and led. The participant Frank Bartleman wrote the line that everyone quotes: that at Azusa Street "the colour line was washed away in the blood."
Parham came to Los Angeles to inspect what his teaching had produced, objected to it in explicitly racial terms as well as on grounds of disorder, and was excluded from the mission.
What happened next
The line did not stay washed away. Within about two decades American Pentecostalism had substantially resegregated into separate white and black denominations, and it remained that way for most of the twentieth century; the formal reckoning with that division did not come until the 1990s, and remains partial.
This is the honest shape of the story and it is more interesting than either half on its own. Azusa Street was a genuine and startling breach of the American colour line, made by a black man teaching a doctrine he had been made to learn from a corridor, and the movement that came out of it reproduced the surrounding society's division anyway, within living memory of its own founding.
The site
There is no building. The mission was demolished in 1938. What stands at the location is a marker, in a district that has since been substantially rebuilt.
That is worth stating plainly rather than apologising for. A tradition which holds that the Spirit is poured out on people rather than lodged in places has, appropriately enough, not preserved its own founding site, and the thing that came out of a converted stable on a short street in Los Angeles is now the fastest-growing part of Christianity on earth.