EU referendum: Derbyshire votes in favour of leaving
Every council area in Derbyshire has voted to leave the EU.
An emotional Margaret Beckett, the Derby South MP, said she would be "surprised" if the United Kingdom was still together in five or 10 years' time.
Toyota, a major employer in the county, said it would "closely monitor" the impact of Brexit on its business.
The closest vote was in High Peak, which voted 50.5% in favour of leave.
Overall in Derbyshire, 59.1% voted leave and 40.9% remain with turnout in most areas above the national average, including Derbyshire Dales, where 81.9% voted.
Andrew Bingham, Conservative MP for High Peak and a Leave campaigner, tweeted: "A truly historic moment, but not a time for gloating or triumphalism, a time for everyone to respect the democratic decision and work together."
But most Derbyshire MPs had campaigned to remain, including Labour's Dame Margaret Beckett.
Holding back tears, she said: "If in five years, 10 years' time we're still a United Kingdom, I shall be very, very relieved but really, very surprised," she said.
"The things of which we have been proudest are now at risk...I'm talking about Rolls-Royce and Toyota."
A Rolls-Royce spokesman said: "We respect the verdict of the electorate, although this is not the outcome we would have chosen.
The firm added it "remains committed to the United Kingdom where we have been headquartered for more than a century, where we have a talented and committed workforce and where we carry out the lion's share of our research and development".
Toyota said: "Going forward we will closely monitor and analyse the impact on our business operations in the UK."
Analysis by Chris Doidge, BBC Radio Derby
It wasn't a landslide, but across the whole of Derbyshire, a clear majority voted to leave.
The public's interest for the question on the ballot paper was clear - turnout was the highest it's been since 1992.
But did the Remain campaign let this slip? Could they have worked harder and achieved a different result?
Locally, their campaign appeared to be lower-key, less well organised and much less enthusiastic than that of the Leave campaign.