Cleveland's final major territorial expansion occured in 1923 with the City's annexation of a neighboring municipality - the 12.5-square mile Village of West Park. Originally a part of Rockport Township and named - not for its western location - but for early settler Benjamin West, the former village stretched from West 117th Street to the Rocky River, south of the City of Lakewood. In addition to Jefferson, it encompassed the neighborhood areas of Kamm's Corners, Puritas-Longmead and Riverside.

During the first two decades of the 20th century, development in West Park was spurred by establishment of "interurban" rail transit service connecting Downtown Cleveland with cities to the south and west via Lorain Avenue. Access to the area was further improved by extension of the Cleveland Electric Railway Company's streetcar line to West 117th Street in 1913 and then to Kamm's Corners in 1923.

Extension of the streetcar line past West 117th spurred development in the Jefferson neighborhood. Both retail and residential development accelerated rapidly during the 1920's. Retail buildings constructed at or near the street line, in order to maximize their convenience to the streetcars, continue to define the character of this portion of Lorain Avenue today. Between 1920 and 1930, Jefferson's population increased from 3,944 to 17,725.

The population of Jefferson also jumped after World War II as area's west of West 140th Street began to develop. These new developments began to take on a more suburban character. Newer shopping plaza's, with unified parking in front, were developed at Fairwood Plaza at Lorain and West 136th and Puritas Plaza (Marc's Plaza) at Puritas and West 150th. The construction of I-90 and I-71, which cross through the north and south ends of the neighborhood, have also created better access and opportunites for office, retail and industrial development.