AutoNation’s longtime chief executive Mike Jackson will step down from the role next year but remain executive chairman until 2021, the largest US auto retail chain said Wednesday.

AutoNation’s stock has more than tripled since Jackson became CEO in 1999 after the company’s founder, Wayne Huizenga, hired him from Mercedes-Benz USA, where Jackson was president.

The Fort Lauderdale, Florida-headquartered retailer has retained its No. 1 position in the US under Jackson’s leadership.

His departure as CEO comes as US automotive sales are cooling down after a solid run for several years following the 2008 financial crisis.

AutoNation said executive search firm Spencer Stuart would support its CEO succession process.