Shennecossett changed significantly over the next few decades, including a redesign by Donald Ross, eventually evolving into a full 18-hole country club.

In 1997, the town performed a "land swap" with the pharmaceutical company Pfizer, losing three holes to the corporation but gaining three along the Thames River and Long Island Sound.

The acquisition of these new holes has, according to Golf Magazine, "turn[ed] the perennially solid muni into one of the deals of the century."

Thomas Avery, descendent of one of Groton's first settlers, established a four hole course on his property with "fairways extending on both sides on his barn and farmhouse.

[1] The club was constructed on territory once occupied by the Pequot and Mohegan Native American tribes.

[2][7] During the early 20th century, Shennecossett hosted a number of significant tournaments including the Connecticut Open, a PGA Tour-level event.

[9] Club pro Smith was also able to attract some of the world's leading professionals to play exhibition matches at Shennecossett, including J.H.

[15] During this era, the town also applied for financial aid from the federal government to buy the course.

[7][18] Golf Magazine praised the addition of these new seaside holes, stating that they helped transform the "perennially solid muni into one of the deals of the century.

[19] In 2004, it was included in Golf Magazine's Thrifty 50, one of the top American courses recreational golfers could play for less than $50.