The Cross Westchester Expressway opened to traffic in December 1960 at a cost of $50 million. Part of the urban Interstate numerology submitted to the American Association of State Highway Officials (AASHO) on August 22, 1958, the State of New York Department of Public Works numbered the Cross Westchester Expressway as Interstate 187 and the New York Thruway west from I-87 at White Plains as Interstate 387. AASHO responded on August 29, 1958 with a spate of recommendations regarding the statewide proposed numbering.
North of NYC your 387 should change to 287 to match N.J. and it should be even numbered since it is a loop. Likewise your 187 should than be 487 since it constitutes a loop connecting with Interstate route at both ends.
Interstate 487 was subsequently redesignated as part of an extended I-287 east from the New York Thruway in 1961.3
An eastern extension of Interstate 287 was proposed by Robert Moses to complete the beltway around New York via the Oyster Bay-Rye Bridge. A 6.1 mile long cabled-stayed suspension bridge across Long Island Sound was envisioned to link the east end of I-287 at Rye with an extension of NY 135 (Seaford-Oyster Bay Expressway). A study for the crossing was released by Moses in February 1966.4
Planning for the Oyster Bay-Rye Bridge halted in 1970. New studies were required following the implementation of stricter environmental legislation by the Federal government in 1970. An Environmental Impact Statement (EIS) was completed in November 1972 for a 16.5 mile long roadway, including the span and approaches between I-95 and NY 25 in Syosset. New York State submitted the mileage for inclusion in the Interstate system under the Federal Highway Act of 1968.4
Residents in Rye, Oyster Bay and other locations along the proposed corridor organized to counter the bridge and extension of I-287. Their efforts and environmental concerns led to formal cancellation of the crossing by Governor Nelson Rockefeller on June 20, 1973.4
The cancellation of the Somerset Freeway in North Jersey in 1982, the proposed alignment for Interstate 95 between Lawrenceville and Metuchen, resulted in an extension of I-287 east from South Plainfield to the New Jersey Turnpike in Edison Township. This segment was previously designated as Interstate 95. The American Association of State Highway and Transportation Officials (AASHTO) approved the renumbering on June 26, 1985.
The final project of the overall 14 mile reconstruction of I-95 between Bronx, New York and Port Chester was the “Last Mile” of the New England Thruway. Costing $135 million, a design-build contract was awarded for work in August 2018. Construction rebuilt the mainline of I-95 between milepost 14.1 and 15.0 with wider shoulders. Improvements at the exchange joining I-95/287 included replacement and realignment of the ramp joining I-287 east with I-95 north. The ramp from Midland Avenue to I-95 north was also realigned.5
Exit 21 from I-95 south to I-287 west was expanded to two lanes. Additional improvements were also made along I-95 northbound at the Midland Avenue Interchange. Bridge work included a replacement of the Grace Church Street Bridge spanning I-95 at milepost 14.46 and rehabilitation of the Boston Post Road overpass, the Purchase Street overpass and I-95 over the Byram River.5 The overall project was completed by November 1, 2021.6