Here is the full list of all 18 Prison Architect achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Escape from a decent prison in escape mode
Have a cashflow of $50,000 or more
Build a sandbox prison with 500 prisoners
Build a sandbox prison with 1000 prisoners
Loaded a prison from Steam Workshop
Stopped a riot of 50 or more prisoners
Achieve a re-offending rate of 25%
Unlock entire tech tree
Build a sandbox prison with 100 prisoners
Complete the story
Complete all optional objectives on Riot
Complete all optional objectives on Conviction
Complete optional objective on Bootstraps
Sell your prison and make over $1,000,000 profit
Executed a prisoner on death row
Unlocked all polaroids
Unlocked all game bible pages
Shared a prison via Steam Workshop