The Anaheim chili pepper is named for the California city of Anaheim. The peppers originated in New Mexico, where they are still grown in different versions. However, they were brought to the city of Anaheim in southern California in 1894 and grown commercially by Emilio Ortega, and remain highly popular today. The Anaheim is a mild variety of the cultivar New Mexico No. 9.
In New Mexico, Anaheim peppers are referred as New Mexico Chilies, or often as the more well known Hatch Chili Pepper, when grown in New Mexico Hatch region.
The Anaheim pepper is a mild, medium-sized chili pepper that grows to 15-25 cm in length. It is often used for cooking and recipes when green, though it can be used when red.The basic variety ripens to a dark green/reddish color, but other strains ripen to full red. They are one of the most common chili peppers in the United States and are used in many foods and recipes. Red varieties can be strung together and dried to make ristras.
Source: https://www.chilipeppermadness.com/chili-pepper-types/sweet-mild-chili-peppers/anaheim-chili-peppers/