A total of 840 channeled (female, n = 388; male, n = 452) and 405 knobbed (female, n = 239; male, n = 166) whelks were measured for shell length (SL) and shell width (SW), with age estimates made from corresponding operculum annual growth striae readings. Gonads (ovary and testis) and reproductive structures [nidamental gland (females) and vas deferens (males)] were assessed macroscopically for maturity stage. All whelks used in this study were collected from Rhode Island state waters within Narragansett Bay, Mount Hope Bay, and Little Narragansett Bay (Pawcatuck River). Data were aggregated by species and sex, with each species treated as a single population within the study area. Age at size (growth rates) and age and size at 50% and 95% maturity were estimated for both species by sex. Female channeled whelk had the highest mean annual growth rates and reached minimum legal size quickest [minimum shell length (MSL) = 136.53 mm, minimum shell width (MSW) = 76.20 mm] and at the youngest age. Male channeled and female knobbed had similar growth rates and were the next quickest to reach MSL and MSW. Male knobbed grew slowest and were the last to enter the fishery and at the oldest age. Estimated age at 50% maturity (A₅₀) for female channeled and female knobbed was nearly the same at 8.46 and 8.35 y, respectively. Male channeled had an estimated A₅₀ of 7.35 y and that of male knobbed was 5.65 y. Estimated size at 50% maturity (SL₅₀ and SW₅₀) for female channeled was 136.8 mm SL and 77.5 mm SW; female knobbed was 124.0 mm SL and 68.4 mm SW; male channeled was 116.0 mm SL and 64.9 mm SW; and male knobbed was 89.4 mm SL and 47.7 mm SW. No instances of protandrous hermaphroditism, pseudohermaphroditism, or imposex were observed. A total of 231 newly hatched (age 0) knobbed whelks were measured for SL and SW, with mean SL and SW at age 0 included in age-at-size (growth rate) analyses.