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