Which chili peppers are dried and become 'chile ancho'?

The poblano ('Capsicum annuum') is a mild chili pepper originating in the state of Puebla, Mexico. Dried, it is called ancho or chile ancho, from the Spanish word 'ancho' (wide).

While poblanos tend to have a mild flavor, occasionally and unpredictably they can have significant heat. Different peppers from the same plant have been reported to vary substantially in heat intensity. The ripened red poblano is significantly hotter and more flavorful than the less ripe, green poblano.

After being roasted and peeled (which improves the texture by removing the waxy skin), poblano peppers are preserved by either canning or freezing. Storing them in airtight containers keeps them for several months. When dried, the poblano becomes a broad, flat, heart-shaped pod called a chile ancho (literally "wide chile" or "broad chile"). These dried ancho chiles are often ground into a powder used as flavoring in various dishes.