KANSAS CITY, Missouri (Reuters) - A devastating drought deepened over the last week in many US areas, spreading through more of the Plains and going into the Midwest as triple-digit temperatures baked already thirsty crops and livestock. The Corn Belt states of South Dakota, Iowa, Illinois and Indiana saw drought develop quickly as the important corn-growing region got only spotty rainfall amid the high heat, according to the weekly US Drought Monitor, produced by a consortium of national climate experts.