Here's an academic paper that I recently came across. It looks at the 19th century Mormon situation, and how anti-Mormon sentiment linked up to Imperialist (and racist) ideas. "The onward march of the North-Western European Peoples" and all that. It'll make you shudder as you read it, but thoroughly fascinating.
TABLE OF CONTENTS
I. MORMON POLYGAMY AND NATURAL LAW AT THE SUPREME
A. The Origins of the Reynolds Litigation
B. The Natural Law Argument in Reynolds
II. IMPERIALISM AND THE REJECTION OF NATURAL LAW IN REYNOLDS.
III. THE AFTERLIFE OF THE IMPERIAL RHETORIC IN REYNOLDS
A. Imperialism and the Anti-Polygamy Crusade of the 1880s
B. Reynolds and Fin de Siecle American Imperialism