How did the divergence between the Wire and Smooth Fox Terrier become formalized?

Breeders selectively bred existing Smooth strains with rough-coated terriers to fix the wiry texture, leading to differentiated standards.

The relationship between the Wire and Smooth Fox Terriers was initially blurred, as they shared a common ancestral pool and were sometimes viewed as variations of one breed. The key driver for separation was the coat texture. Breeders dedicated to the wiry look intentionally crossed existing Smooth strains with other rough-coated terriers to fix and establish that harsh texture. As this preference solidified, breed standards began to be written that formally differentiated requirements based on coat type, ultimately leading to their establishment as two distinct breeds, even though their core temperament remained shared.