As one of the leading CPA firms on the North Shore, Ambrosi Donahue Congdon traces its roots back to 1974. At that time, Tom Ambrosi, formerly associated with Touche Ross & Co. of New York, started practicing in Newburyport. In 1977, he partnered with Mike Donahue of Arthur Andersen & Co. of Boston to establish Ambrosi Donahue & Co., P.C. In 1979, the firm acquired the local practice of George K. Leavey, P.A. and flourished in its State Street, Newburyport offices.

With continued growth of the firm, Ambrosi Donahue renovated a historic brick building near the corner of State and Harris Streets in 1982. The firm expanded its client base throughout the lower Merrimack Valley, seacoast New Hampshire, and southern Maine. In 1997, Ambrosi Donahue & Co., P.C., merged with the practice of Keith N. Congdon, CPA, an international accounting, audit and tax practice with considerable corporate and accounting expertise. Keith began his career with Coopers & Lybrand in Hartford, Connecticut.