Museum specimens of the Great Plains Ratsnake (Pantherophis emoryi) from six counties in northern Kansas were examined to determine gonadal cycle, clutch characteristics, and body sizes at sexual maturity near the northern edge of its geographic range. Gonadal cycle of males of northern Kansas adhered to a temperate pattern unlike that of Eastern Corn Snakes (P. guttatus) of southern Florida, whereas females of both species from these locations maintained a tropical pattern to their monthly distribution of follicle size. Clutch size averaged 9.5 eggs in this study and 7.2 eggs in a study of this species in northeastern Kansas. Both of these values were smaller than those of southern and eastern populations of the Eastern Corn Snake despite larger or similar body sizes, respectively, of the latter group. We discuss the potential effects of climate change on male reproduction and clutch size.