Westerlo is a town in Albany County, New York, United States. The population was 3,194 at the 2020 census.

New York State Route 143 (NY 143) is a 18.82-mile-long (30.29 km) state highway in Albany County, New York, in the United States. The highway runs from an intersection with NY 85 in the town of Westerlo to a junction with NY 144 in the hamlet of Coeymans. The entire route is two lanes wide. NY 143 follows the path of the Coeymans and Westerlo Plank Road, a plank road that operated from 1850 to the early 20th century. The road became a state highway by 1915 and was designated NY 143 as part of the 1930 renumbering of state highways in New York.