The highway has developed sporadically since the 1970s, with the 2-lane controlled access portion to Bridgewater being largely responsible for the abandonment of
CN Rail's South Shore line, the former
Halifax and Southwestern Railway. In November 1998, construction was completed that twinned a five kilometer section of highway between exit 2 and exit 3. In November 2006, construction was completed that twinned 15 kilometres of highway between exit 3 and exit 5. In December 2006, an 8.3 kilometre bypass around
Barrington was completed. In late September 2015 a new section of highway was opened to bypass the Port Joli area. In November 2016, a new section was completed which bypassed Port Mouton. Residents complained that the single exit east of the community had lengthened the trip for people heading west from Port Mouton. The new interchange in Ingramport (exit 5A) opened in January 2017. Work on twinning Highway 103 from exit 5 (Tantallon) to exit 5A (Ingramport) began in February, 2018 and was completed in December, 2020. Twinning from exit 5A (Ingramport) to exit 6 (Hubbards) started in 2020 and was completed in July of 2024. Construction on the twinning from exit 6 (Hubbards) to exit 9 (Chester) is underway. ==Names of Highway 103==