Hard to say whether this serious-looking group is enjoying what must have been a day trip to Thacher Island. It looks like they might have just finished lunch, as there seems to be some sort of pot on the ground and two boys in the background are swigging something from bottles. The man on the left is leaning against the base of one of Thacher’s twin lighthouses, and it looks like there is an umbrella or two also leaning against the base.
This is a real-photo postcard, meaning that it was printed on postcard stock directly from a negative and not through a commercial printing process. Real-photo postcards can be one of a kind or one of several printed from the same negative.
The inscription on the left tells us that this photograph was taken on Aug. 7, 1906, and notes that Thacher’s lighthouses were first lighted in December 1771 (although the present-day granite towers were not completed until 1861).
The card was mailed from Boston, Mass., to Geneva, N.Y., on Jan. 3, 1907.
Vintage Rockport 
CHECK OUT THOSE HATS THOSE WOMEN ARE WEARING…..LET THE GOOD TIMES ROLL…
They are picnicking in the only shady place on the island in the shadow of the south tower.Note the tramway trestle on the right going to the roof of the whistle house(not shown).The oil house is directly behind the woman on the far left. The man standing could be the keeper Addison Franklin Tarr who served from 1876 to 1912 longest ever 36 years.These people could have been relatives.He probably told them the only shady place is next to the south tower. In these year the island was barren of any vegetation.
Thanks for your insights Paul.