Last week, the Pennsylvania Department of Corrections (DOC) celebrated the opening of its newest prisons. Called SCI Phoenix, the project took more than a decade to complete, cost more than $400 million dollars, and will house almost 4,000 people. It is the second most expensive construction project in Pennsylvania's history.

Over six years ago, before the walls and razor wire went up, I was arrested – along with others – for trying to physically block the project from moving forward. And I was one of thousands of people, inside and outside of prison, who took action to stop the expansion of Pennsylvania's prison system.

The controversial prison construction was initiated more than a decade ago by then-Gov. Ed Rendell, and seems a perfect symbol for Pennsylvania's destructive and devastating relationship with mass incarceration. Over the last three decades, the state has invested massively in putting its own residents in cages — from about 8,000 people in 1980 to about 50,000 today. The corrections budget now tops $2.6 billion. Families and communities across the state are suffering because loved ones are behind bars.

How did we get here? Not because Pennsylvanians were committing more crimes, but because lawmakers in Harrisburg were more invested in political expediency than in actual justice. They passed mandatory minimum sentencing policies and harsh penalties for a wide variety of offenses, and approved seemingly endless funding for prison construction. These policies disproportionately targeted poor people and people of color.

Mass incarceration has come at a terrible cost to Pennsylvania's communities. Rather than keeping people safe, these policies fuel cycles of violence. Philadelphia has an alarmingly high incarceration rate, but hundreds of people are killed by gun violence every year. Clearly, prisons are not an effective response. They neither address the needs of survivors of harm nor alleviate the root causes of violence.

Phoenix faced mass opposition before ground was even broken. Thousands of people implored their state legislators, the governor, and the DOC to cancel the project. Many people incarcerated at Graterford and elsewhere spoke out against the proposal. Even the Department of Corrections' own projections indicated that the prison population was decreasing; after years of "tough-on-crime" policies, there was finally modest momentum around sentencing reform. It seemed like an ideal time to not build new prisons.

In 2011, sweeping cuts were announced to public education, general assistance, and other critical social services. Despite massive movements demanding that the state fund schools, not prison expansion, politicians refused to stop construction.

Finding no traction in Harrisburg, Decarcerate PA – a grassroots campaign that was formed to stop prison expansion and work toward decarceration and community reinvestment – decided to take a more direct approach. In November of 2013, several of us blockaded the access road to the prison construction site using school desks, a model school house, and our bodies.

While we stopped the construction for only a few hours, the action raised the visibility of the project and generated public outrage. Several months later, protesters marched 113 miles from Philadelphia to Harrisburg to demand cancellation of the project. We met with legislators, community leaders, journalists, and people across the state. And still, construction continued.

Now, the doors of Phoenix are about to open. Or more accurately, they are about to shut behind the 3,830 people who will be imprisoned there.

When this prison expansion project was proposed more than a decade ago, it was presented as a solution to the urgent needs of an overcrowded prison system. But time-intensive infrastructure projects do not provide immediate solutions. They are blueprints for the kind of future we envision.

What if, in 2008, we had not asked "how do we create space to warehouse more prisoners," and instead posed the question, "how do we end this crisis of mass incarceration"? If instead of spending more than $400 million on razor wire and concrete, we had invested that money in programs that addressed the root causes of violence? If politicians had the courage to imagine a future that did not need more cages, if we had invested in a future that honored the rights and dignity of all people, where could we be in 2018?

It's too late to change the past. But our efforts to change the way Pennsylvania thinks about prisons continue. We've built a strong movement that has pushed for – and won – real changes in Pennsylvania's criminal legal system. We've seen longtime activists from behind the walls come home from prison and join the work out here. We stopped construction of a new jail in Philadelphia, and now the mayor has committed to closing House of Correction – though he has yet to commit to demolishing it.

SCI Phoenix is a tragedy, and one we must make sure is never repeated. These must be the last new prisons Pennsylvania ever builds. Let's invest in the future we want to inhabit.

Layne Mullett is a founding member of Decarcerate PA, a grassroots organization working to end mass incarceration in Pennsylvania.