The number of lives saved was calculated by the Coast Guard historian's office through research of logs and records from the Coast Guard, the Revenue Cutter Service, the US Life-Saving Service, the Lighthouse Service and other agencies that eventually became the modern Coast Guard. In addition to tallying the total number of lives saved, the historian's office has compiled a list of the top ten rescues in the Coast Guard's history. The list shows the breadth of the Coast Guard's efforts to save lives in peril on the seas for over 217 years.
See the link for more info and the Coast Guard's Top 10 rescues.
It would be great to see a similar list at the Auxiliary History web site. The Auxiliary rescue of 13 in Alaska this past April comes to mind, as well as the rescue of five family members from a canoe on the Delaware River last August.