Mack-Cali Corp., a real estate company best known for North Jersey offices, says its Roseland apartment division will seek city approval to build 300 apartments in a new 32-story tower in the vacant lot at 709 Chestnut St., near Independence Hall, in partnership with the site landowner, the Zuritsky family's Parkway Corp., with construction expected to start by the end of 2015.

Mack-Cali in 2013 said it was shifting its Philadelphia-area focus from its aging suburban offices to apartments and mixed-use development, reflecting both the region's flat office rents, and also growing higher-end residential demand in Center City and other transit-friendly neighborhoods.

In a statement Wednesday, CEO Mitchell E. Hersh called the proposed 709 Chestnut tower, on a block best known for restaurants (like Jose Garces' Rosa Blanca down the block, or Stephen Starr's Jones across the street), "a cornerstone of the burgeoning Market Street East neighborhood, which is quickly emerging as a dynamic cultural destination in a previously underutilized corridor." He expects to draw young "millennial" tenants as well as older "empty nesters."

The proposal includes an automated 125-car garage, similar to the one Parkway built in another residential tower at 1706 Rittenhouse Sq.  Roseland says it is also seeking other sites in and around Philadelphia for "active reuse." The company also plans, for example, to add apartments in the former Curtis Pubishing Corp. headquarters (now offices) nearby, in partnership with Keystone Property Group, which has purchased dozens of former Mack-Cali office buildings in Philadelphia's western and South Jersey suburbs.

Mack-Cali and Parkway are also partners in redeveloping the former Rohm and Haas office building at 100 Independence Mall West, where they say they have invested $20 million in a new 110-unit parking garage, Independence Beer Garden and other retail additions.