A male, 18 month old adult capable of breeding can be as small as 14 inches. Females can be up to 3 years old, sexually mature and ready to breed, at only 16-18 inches. I'll bet my miss piggy at around 2 feet, is already 4-5 years old and has had several litters in her lifetime so far. She's big for a northwestern.

After about 25 years of herping, the largest female northwestern I ever found (just last summer) was 2.5 feet long. She was at the end of her life and unusually large. Nearly a foot longer than what they normally top out at.

The point is, Northwesterns are the smallest species of garter. Litters are small, they are born small, and they don't grow to adult size very fast. They take their time. And yet, they are the most commonly encountered reptile where they occur.