Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

1919  Congress passed the National Prohibition Enforcement Act, otherwise known as the Volstead Act, on this date.  The Volstead Act authorized the enforcement of the 18th Amendment, ratified on January 29, 1919.  The Act authorized the Coast Guard to prevent the maritime importation of illegal alcohol.  This led to the largest increase in the size and responsibilities of the service to date.

USS LST-71 at anchor in the harbor at Fiji, 12 September 1943.
6th Special Navy Construction Battalion (N.C.B.) Photo

1943  Choiseul, Treasury Islands landing commenced (Coast Guard-manned LST-71 was in second echelon November 1, 1943).

1966  Coast Guard LORAN Station Con Son in Vietnam became fully operational.

More details
Original caption: “Gitmo airfield converted for 10,000 migrants”

1991  Thousands of Haitian migrants began fleeing their homeland after the overthrow of Haitian President Jean-Bertrand Aristide, prompting one of the largest SAR operations in Coast Guard history.  Cutters and aircraft from as far north as New England converged on the Windward Passage.  In the first 30 days of the operation, Coast Guard forces rescued more than 6,300 men, women, and children who left Haiti in grossly overloaded and unseaworthy vessels.  Seventy-five Coast Guard units ultimately took part in the massive SAR operation and by the end of the year over 40,000 Haitian migrants were rescued.

Tsunami warning after 7.7 earthquake off Haida Gwaii (Queen Charlotte Islands)

2012  The Coast Guard Captain of the Port of Honolulu ordered the evacuation of Honolulu Harbor after a tsunami warning was issued after an earthquake struck the Haida Gwaii archipelago in western Canada.