Cooper's first naval assignment came on March 21, 1808 aboard the , an 82-foot bomb ketch that carried twelve guns and a thirteen-inch mortar. For his next assignment, Cooper served under Lieutenant Melancthon Taylor Woolsey near Oswego on Lake Ontario, overseeing the building of the brig for service on the lake. The vessel was intended for use in a war with Great Britain which had yet to begin. The vessel was completed, armed with sixteen guns, and launched in Lake Ontario in the spring of 1809. It was in this service that Cooper learned shipbuilding, shipyard duties and frontier life. During his leisure time, Cooper would venture through the forests of New York state and explore the shores of Lake Ontario. He occasionally ventured into the Thousand Islands. His experiences in the Oswego area later inspired some of his work, including his novel "The Pathfinder".