New Haven broke ground on Phase 1 of the Downtown Crossing project last Friday, marking the beginning of the city’s attempts to reunify its urban communities.

Attended by Mayor John DeStefano Jr., U.S. Rep. Rosa DeLauro, Gov. Dannel Malloy as well as several business and community leaders, the event followed an announcement earlier this month that the city was prepared to begin the project, which has been many years in the making. Centered around the removal of Route 34 — a highway that separates the Hill neighborhood in the city’s south from downtown — the Downtown Crossing project aims to bridge existing divisions between blocks and to stimulate the city’s economy with new housing and retail facilities.

The undertaking, which will close streets in the area as construction proceeds, is expected to span seven years. The first phase involves the construction of a 426,000-square-foot medical building at 100 College St., which will house, among other tenants, the offices of Alexion Pharmaceuticals.

“Today, we are reclaiming part of our city,” DeStefano said at the groundbreaking. “The ditch we are now standing in will once again be turned into a thriving, vibrant neighborhood.”

Route 34 was constructed in the 1950s as a part of the era’s Urban Renewal movement, when city planners demolished the Oak Street neighborhood, considered a slum at the time, displacing over 1,400 families and destroying hundreds of buildings in an attempt to eradicate inner-city poverty and build new city infrastructure. But the Urban Renewal philosophy, which did not yield the expected tax revenue and largely failed to lift families out of poverty, is now considered to have been a mistake.

A crowd gathered to witness the official start to the massive construction project — set to correct the wrongs of Urban Renewal — which DeLauro said has been anticipated for over 30 years.

“Seeing the new Downtown Crossing take shape is special. I remember first working on this project over 30 years ago, and am proud to have seen it through to this point.” DeLauro said.

Ward 7 Alderman Doug Hausladen ’04 estimated that there were about 40 to 50 people at the event, including a significant number of people from New Haven’s business and political communities. He said the day was a “great celebration, marking the culmination of a lot of work and the start of a lot more.”

Irving Adler, Alexion’s executive director of corporate communications, expressed excitement about the groundbreaking ceremony. He added that he looks forward to the move that the construction project will facilitate, as the company’s headquarters will relocate to its new building from its current location in Cheshire, Conn.

“The company is pleased to provide the foundation for a growing biotechnology industry in New Haven, and to work in an area that is heavily focused on education and academia including Yale’s medical campus and the Yale-New Haven Hospital,” Adler added.

The state government has invested over $30 million to foster economic growth in New Haven, Malloy said at the ceremony. He called the project an “ambitious reimagining” of the city, adding that he is committed to firmly rooting Alexion into the fabric of the community.

According to city officials, the project’s first step will involve connecting Route 34 with the existing street grid. The plan will also reclaim 10.5 acres currently occupied by the highway and redevelop the space, merging residential and commercial facilities with streets easily accessible by all forms of transportation.

Phase 1 of the Downtown Crossing project will be partially funded by a federal Tiger II grant, which is designated for economically beneficial transportation projects.