Who invented the hairbrush?

The earliest U.S. patent for a modern hairbrush was by Hugh Rock in 1854.

A brush with elastic wire teeth along with natural bristles, was patented by Samuel Firey in 1870 as U.S. Patent 106,680.

Lyda O Newman, an African American, improved the hair brush to make it ventilated and easier to clean. Her patent date was November 15, 1898. Nothing in her patent says she was the first to invent a hair brush, nor that she was the first to use synthetic bristles.
Lydia O. Newman patented the brush in 1898