What is the fine-grained topic of the following text: Forgotten Heroes, The U.S. Life-Saving Service on the Great Lakes – From 1874 until 1915 when it became the U.S. Coast Guard, the men of this remarkable organization displayed incredible courage and bravery in rescuing over 55, 000 people from potential death on the Great Lakes. Only return the topic.
The U.S. Life-Saving Service's operations and heroism on the Great Lakes from 1874-1915.