Ruth Landon did a tremendous amount of deed research for many years. She did not publish but the Kennebunkport Historical Society has her notebooks. They are alphabetical binders by name containing her notes on early settlers. I'm sure she has a section in one of her notebooks on Merrill.
Sketch of Kennebunk Port 1850 This is an article from The Portland Transcript in 1850 describing Shipbuilding, beaches, pleasure boating, churches etc. I found this newspaper article for $8 at Dewolfe and Wood when I was writing the story on D&S Ward. In it I learned that in 1850, a year before the brothers had purchased the land below the So Congregational Church, they already had a large steam mill and were actively engaged in shipbuilding.
1861, 1871 and 1891 Maine Register Lists names of Postmaster, Selectmen, Physicians, Clergymen, Merchants, Manufacturers etc. for that year
1872 Kennebunkport Directory from York County Atlas http://www.mykennebunks.com/maps.htm
Leading Business 1888 Detailed description of businesses and businessmen of Kennebunkport and Kennebunk and a historical sketch of each town.
1905 York County Register
1907 Kennebunk and Kennebunkport Directory Includes every head of household in 1907, listed alphabetically with the name of the street they live on. Also describes all businesses, professional people and associations.
1919 Who's Who of Kennebunkport Kennebunk Beach Cape Porpoise and Beachwood Mostly cottagers. Lists people alphabetically includes winter address. Some photos
All of the State Registers are also available at the Springvale Library.