Interstate 781

Interstate 781 (I-781) is an auxiliary Interstate Highway north of Watertown in Jefferson County, New York. The route extends for 4.3 miles (6.9 km) from an interchange with I-81 in Pamelia to the main entrance of Fort Drum in Le Ray. It also has one intermediate interchange with US Route 11 (US 11) just west of Fort Drum. I-781 is four lanes wide and serves as the principal travel corridor into and out of the post. The freeway is ceremoniously designated as the Paul Cerjan Memorial Highway in honor of Paul G. Cerjan, a late US Army lieutenant general who oversaw a $1.2-billion (equivalent to $3.73 billion in 2023) expansion of Fort Drum in the 1980s.

The original designation for I-781 was New York State Route 781 (NY 781). On April 13, 2009, the Federal Highway Administration (FHWA) designated NY 781 as a future Interstate Highway corridor and as "Future I-781". The I-781 designation officially took effect when the highway was completed and opened to traffic on December 6, 2012.