Once a desolate strip hugged by slightly forbidding warehouses, factories and garages, Union Avenue just north of the Brooklyn-Queens Expressway has seen a significant transformation in recent years into the sort of glass-lined thoroughfare more typically found in trendier parts of Williamsburg, Brooklyn.

Three new sizable developments around Union Avenue, North 10th Street and Frost Street are adding almost 425 rental apartments and more than half a dozen new stores along Union Avenue. A small condo project nearby at 538 Union is also in the planning stages, said David J. Maundrell III, the president of aptsandlofts.com, which has been marketing apartments in the area.

The buildings are a natural extension of the high-rise development that took place almost a decade ago a few blocks north on Bayard Street, bordering the southern side of McCarren Park, said David A. Sigman, an executive vice president and principal of LCOR, which has developed 234 units at 250N10, a six-story glassy building at North 10th and Union.

“A lot of this is drifting down from what happened originally at Bayard, kind of driven by the park, and probably helped along by the renovation of the park and the pool,” Mr. Sigman said. “That’s your anchor to the north.”