State-sponsored construction of a half-mile parkway at Union Point has begun, improving access to one of the largest undeveloped parcels in Greater Boston and prompting new hopes of economic development after two decades of false starts.

A new $6.7 million roadway, scheduled for completion in November, is the last link of an east-west connection across the base from Route 18 in South Weymouth to Rockland near Route 3. The 1.8 mile Bill Delahunt Parkway was completed in 2013 along the eastern side of the property.

The Union Point site spanning 1,400 acres in Abington, Rockland and Weymouth has approvals for 6 million square feet of commercial development and 3,900 housing units. The former South Weymouth Naval Air Station closed in 1997.

LStar Communities is the latest in a line of master developers seeking to jumpstart development on the site. Plans call for a mixed-use town center to be built along the new roadway including 800 housing units near the MBTA station.

Braintree developer John M. Corcoran and Co. acquired 5 acres for $12.6 million last month at Union Point for a 265-unit apartment complex, The Patriot Ledger reported.

“By completing this parkway, and linking the existing Delahunt Parkway to the South Weymouth commuter rail station and Union Point’s future town center district, we are spurring the creation of new transit-oriented housing, restaurants, shops and employment opportunities for the South Shore,” Housing and Economic Development Secretary Jay Ash said during a ceremony Thursday.

The property had been known as SouthField until being renamed by LStar in July as Union Point. In March, LStar announced plans for an $8 million park and recreation complex on 25 acres.