343 Commonwealth was designed by Bradlee, Winslow, and Wetherell, architects, and built ca. 1882 as the home of George Glover Crocker and his wife, Annie Bliss (Keep) Crocker. He is shown as the owner on the 1883, 1888, 1898, 1908, and 1912 Bromley maps, and was the assessed owner through 1916. They took occupancy by the 1883-1884 winter season, having previously lived at 74 Boylston. They also maintained a home in Cohasset.
George Crocker was an attorney. He was a Massachusetts State Senator from 1880 to 1884, and subsequently served as a member of the Massachusetts Railroad Commission.
He died in May of 1913. Annie Crocker continued to live at 343 Commonwealth until her death in September of 1929. She is shown as the owner on the 1917 and 1928 Bromley maps, and was the assessed owner through 1929; her heirs were the assessed owners in 1930. She also continued to maintain a home in Cohasset.
343 Commonwealth was not listed in the 1930-1937 Blue Books.
In July of 1931, the Garland School of Homemaking (later to become Garland Junior College) acquired 343 Commonwealth from the Institution for Savings in Roxbury. It had acquired 341 Commonwealth one month earlier.
Both properties were shown as vacant in the 1931-1933 City Directories, but had been converted into dormitories by 1934.
By the late 1960s, Garland Junior College had assembled a portfolio of 22 properties in the western portion of the Back Bay: 315, 319, 321, 329, 337, 339, 341, 343, 349, 377, 407, 409, 411, 413–415 Commonwealth, 24 Charlesgate East (419 Commonwealth), and 447, 449, and 451 Marlborough (composed of 451-457 Marlborough).
In April of 1976, Garland Junior College announced that, because of financial difficulties, it was merging with Simmons College. It subsequently sold twelve of its properties and transferred the remainder — those located furthest west (407-415 Commonwealth, 24 Charlesgate East, and 451 Marlborough) — to Simmons College.
Glen G. Grant, trustee of the Commonwealth College Trust, purchased eleven of the twelve properties that Garland Junior College sold. In October of 1976 he purchased 315 and 341 Commonwealth, and 447 and 449 Marlborough; in January of 1977, he purchased 319, 321, 329, 337, 339, 343, and 377 Commonwealth. The remaining property, 349 Commonwealth, had been purchased in September of 1976, by Andrew Saggese, Jr., trustee of the Drew Realty Trust.
In May of 1980, Glen Grant transferred 315, 319, 321, 337, 339, 341, 343, and 377 Commonwealth to Judith S. Schwartz, trustee of Seofon Trust (the deed was dated in May of 1980 but recorded in June of 1981).
In May of 1981, the Commonwealth College Trust filed for permission to convert 343 Commonwealth from a dormitory into seven apartments, which it stated was the existing use. It subsequently abandoned the application.
In May of 1982, Judith Schwartz sold 319, 321, 337, 339, and 343 Commonwealth back to Glen Grant and Mac C. Grant.
In June of 1983, they transferred 319, 321, and 343 Commonwealth to Dorothy F. Wirth, trustee of the 337-339 Commonwealth Avenue Trust.
In November of 1983, the 337-339 Commonwealth Avenue Trust applied for (and subsequently received) permission to convert 343 Commonwealth into eight apartments, which it indicated was the existing condition.
In January of 1984, the 337-339 Commonwealth Avenue Trust converted 343 Commonwealth into seven condominium units, the 343 Commonwealth Avenue Condominium.