Fourteen years after the marriage of Nashville’s two largest assisted-living companies — American Retirement Corp. and National Retirement Corp. — the combined company is acquired by Brentwood-based Brookdale Senior Living for $1.2 billion in cash.

The move sends shockwaves through the sector, as American Retirement Corp., founded by HCA cofounders Dr. Thomas Frist Sr. and Jack Massey, has been an industry leader for almost four decades.

Eight years later, Brookdale will cement its place as the largest national provider of senior living after merging with competitor Emeritus Senior Living.