 The portion of modern NY 340 south of Sparkill was originally designated as part of US 9W in 1927.At the time, US 9W continued south into New Jersey on what is now CR 501 and north from Sparkill on its modern alignment.By 1929, US 9W was realigned near the New York–New Jersey state line to run along the Hudson River from Fort Lee, New Jersey, to Sparkill.