After working with fine-dining chef Jeremiah Tower at Stars in San Francisco, Ells opens the first Chipotle in Denver.

With 16 restaurants open, Ells sells a minority interest in the company McDonald’s Corp., which helps with expansion capital and management.

Chipotle reaches 560 units.

Chipotle makes its initial public offering, priced at $22 share and rising within one trading day to $44 a share; McDonald’s divests its one-time 90 percent interest in the brand.

Chipotle opens its first ShopHouse Asian Kitchen in Washington, D.C., applying the Chipotle fast-casual line-service model to Asian food.

Chipotle invests in the fast-casual Pizzeria Locale in Denver.

Chipotle’s stock reaches its all-time high of $754.03 on Aug. 17, 2015.

Chipotle restaurants in Minnesota experience a salmonella outbreak on Sept. 11.

Chipotle temporarily closes 43 restaurants on Oct. 31, in Washington and Oregon, after an E. coli outbreak. They reopen Nov. 10.

Chipotle closes a Boston location after a suspected norovirus outbreak, and later in the month the Centers for Disease Control investigate suspected outbreaks in Kansas, North Dakota and Oklahoma.

Ells appears on “The Today Show” to apologize for the string of illness outbreaks.

On Dec. 23, Chipotle outlines new cooking methods in an effort to prevent future foodborne-illness outbreaks.

Chipotle announces it will shutter its 15-unit ShopHouse Asian Kitchen division.

Chipotle shares close at a five-year low of $268.70 on Oct. 30 after third-quarter revenue and same-store sales came in below analyst expectations.

Chipotle on Nov. 29 announces Ells will step down as CEO and shift to executive chairman after a successor is named.