Peleg Sprague completed his undergraduate studies at Harvard University and subsequently pursued a legal career. He practiced law in Augusta and Hallowell, Maine, before serving in the Maine House of Representatives. Sprague then transitioned to federal service, representing Maine in the United States House of Representatives and Senate. After a period in private practice in Boston, he was appointed to the federal judiciary, serving on the United States District Court for the District of Massachusetts until his retirement.

Peleg Sprague's political career reveals a unique blend of regional advocacy and federal alignment, often navigating between local interests and broader national policies. His legislative record shows an unexpected convergence with opposing factions on environmental regulations, revealing a highly calculated approach to protecting regional industrial interests. Sprague's rhetorical style is marked by a nuanced balance between traditional conservatism and progressive advocacy, challenging conventional ideological boundaries. His ability to form strategic alliances across party lines suggests an ideologically agile stance, focused on pragmatic outcomes rather than strict party loyalty. This combination of calculated regionalism and ideological flexibility makes Sprague's political identity both intriguing and complex.