The 500-acre area off Rusper Road will eventually have 2,750 homes, schools, shops, businesses, community facilities and green open spaces.
Liberty Property Trust was granted outline permission by Horsham District Council for the development - on former agricultural land - but sold the land in 2019 to Legal & General who are now responsible for overseeing it.
Following construction of roads, the new purpose-built Bohunt Horsham school was the first building to go up.
It opened in January this year and will eventually provide places for 1,620 pupils aged from 4-16, along with a nursery for 50 children.
A new footbridge is being constructed over the A264 to link areas south of the town to the new school and rest of the development.
It is expected to open this summer.
The first 390 houses - built by CALA Homes which was acquired by Legal & General in March 2018 - are set to go on sale this spring before other houses are built in phases.
Meanwhile, supermarket chain Morrisons is planning to build a new store in the development area, which has now been formally named Mowbray Village.
Legal & General say that the name Mowbray was inspired by the heirs of Geoffrey de Montbray, an advisor to William the Conqueror.
Geoffrey’s family were entrusted with the village of Horsham back in the 14th century when they married into the de Braose family, who had been gifted the ancient manor of Horsham by William the Conqueror.