As with Carnegie libraries, the upkeep and maintenance of the library was the responsibility of the town. More information is available online about the history of Sanford's Library -- doesn't mention my name however.
There are three other Maine library postcards in my collection, two of them are of the same library at different times and it is a (unofficial) Carnegie Library.
Augusta Maine. Lithgow Library c1911 above, below c1940New England Carnegies or Wikipedia's List of Carnegie libraries in Maine, the history of the Library states "Andrew Carnegie donated $9000" in 1894 and the library was designed by Neal and Hopkins Architects of Pittsburgh.
Belfast Public Library and Methodist Church. Belfast Maine c. 1900
Not a Carnegie Library, although I couldn't find any information about the history.
Although my current collection of Maine Carnegie Library cards is zero (one unofficial), there were 18 (19) public libraries and two academic libraries built in Maine from grants awarded by the Carnegie Corporation. Obviously I need to do more research on Carnegie Libraries and find an authoritative list.
Carnegie Libraries in Maine = 21
Catherine's collection = 1
Find more Maine library postcards at this website: Maine Library Postcards