[1] After Mary's death in 1891, Searles was left with his wife's vast real estate holdings in San Francisco, New York, Great Barrington, and Methuen, and $21 million.

During the remainder of his life, he satisfied his love of architecture by building a number of grand structures, frequently in collaboration with architect Henry Vaughan.

Collaborations with Vaughan include: He was also an environmentalist and would alter the construction course of a major stone wall so as to preserve a tree that he deemed important.

According to the City of Methuen:"Today, the trio’s collective vision can be seen in mills, housing, schools, mansions, churches, monuments, playgrounds, the library, and the architectural fantasies that resulted from their artistic rivalry.

The historic district boundaries were established to include properties and buildings constructed or used by the Searles, Tenney and Nevins families and the people who worked for them.