What’s the historic I-579 Cap Project all about? We break it down for you.

The first phase of the Lower Hill redevelopment project, the Penguin’s broad overhaul of the 28-acre lot next to PPG Paints Arena, is underway.

Though the footprint for this phase is small, the wider cultural and political statement is significant. Here’s what you need to know:

What is the first phase of the redevelopment, exactly?

Work has begun on a three-acre park that will bridge the Crosstown Expressway, connecting Bigelow Boulevard and Centre Avenue. Known as the I-579 Cap Project, the public park will include paths for pedestrians and bikers, plus rest areas and an outdoor classroom designed by a team of local artists.

It’s also meant to help the environment. According to a press release, the project will provide improved stormwater management with increased green space and the installation of six new rain gardens in cooperation with ALCOSAN.

A wide array of state and local leaders were on hand to celebrate the groundbreaking on Friday, including Mayor Peduto, Governor Tom Wolf and Congressman Mike Doyle.

“I’m proud to have been part of the successful effort to secure more than $20 million in federal funding for this important initiative, and I’m looking forward to the Cap bringing jobs, opportunity and prosperity to the Hill District,” said Congressman Doyle at the event.

Total cost for the park, scheduled to open in 2022, is $32 million via a combination of federal grants, local support and charitable donations.

Here’s good news: The project leaders have said the construction won’t disrupt traffic along the expressway.

“The Commonwealth is proud to be a partner with this important project that rights a decades-old wrong and will provide a vital connection to Pittsburgh’s Downtown for its neighbors,” said Governor Wolf.

Which “decades-old wrong” is the governor talking about?

He means the construction of I-579 in 1956, one of the most infamous examples of racist public policy in Pittsburgh’s history. During the construction, more than 8,000 residents and 413 businesses were displaced, and pedestrian access between the Hill and Downtown vanished.

That physical separation, along with decades of discriminatory public policy, effectively sapped much of the wealth and prosperity from one of the city’s most vibrant and iconic African-American neighborhoods.

“This project not only helps restore the ties once broken between the Hill District and Downtown,” said Mayor Peduto, “but makes promises to the next generations of Pittsburghers too, with opportunities for healthy and walkable communities, and green-friendly design.”

What about the rest of the development?

Exact dates have not been set, but expect to see more cranes and construction equipment near PPG Paints Arena in the near future.

According to the master plan released this March, local development company Intergen Advisors will break ground on 250 units of rental housing sometime this fall, the first of a projected 5oo units. Per the agreement with the city, 20 percent of those units will be affordable for Pittsburghers making 80 percent of the area median income.

And starting this winter, the Delaware-based Buccini/Pollin Group is scheduled to begin construction on office and retail space along Centre Avenue. Discussions with potential tenants are ongoing, and the plan projects 200,000 square feet of offices with 50,000 square feet of retail.