Looking for story - 19th century San Francisco, boxer works for police and/or mob

[rkimmelerre]

If I recall correctly, the main character starts in Boston. Definitely the East coast. He makes money fighting. He leaves town, I believe he gets involved with a carnival or circus for awhile, and ends up in San Francisco. I’m 99% sure it’s SF because a Chinese mobster plays a big part. The MC becomes a cop, I think, and clashes with the mobster. He ends up in love with the mobster’s wife, living in a house she had a painting of.