I'm looking for a picture of the exterior of 349 West 48th St, New
York City, in the mid to late 1950's that shows a semi-circular sign,
JFK MID-CITY DEMOCRATS PLAZA 7-2270.  The sign measures 47"W x 21"H. 
I believe this was Kennedy's first pre-presidential political
headquarters in mid-town, NY.

I'd try contacting the JFK library in Boston.  Here's a description of
their pre-presidential photo holdings:

BERINSKY,  BURTON  1931-91
Photographs 1960-68
Photographs of John F. Kennedy's Presidential campaign in the 
Northeast, his inauguration, and trips as President to New York City. 
Includes extensive documentation of Robert F. Kennedy's senatorial 
campaign and Presidential campaign as well as the March on Selma, 
Alabama (1965) and the 1968 New Hampshire Presidential primary 
campaign, b/w & color. 30,671 items. Permission required to 
reproduce.  

http://www.jfklibrary.org/stillphoto.htm

          -welte-ga