Historic tourist attractions across Scotland generated £2.3 billion and brought 16 million visitors to the country last year, according to an audit.
The industry also supported more than 40,000 full time jobs, Historic Scotland said.
The economic and cultural impact of castles, battlefields, historic houses and gardens has been analysed in the Scottish historic environment audit.
It found that the sector generates 2.6% of total revenues in the country and accounts for 2.5% of employment.
The audit, which was last conducted in 2010, included five world heritage sites including the Royal Mile, 8,205 monuments and attractions such as the Wallace Monument, as well as numerous battlefields, national parks, historic houses and gardens.
Culture Secretary Fiona Hyslop said: "The significant impact and contribution of the historic environment sector to Scotland's economy, society, education and cultural identity is confirmed and outlined within this updated audit.
"We have clear evidence that our historic environment is a major contributor not only to almost every community in the country, but has a major bearing on how we are regarded internationally.
"With the wealth of history and heritage we have in Scotland, we are well placed to capitalise on the growing interest for this sector."
The audit found that a fifth of school trips are to historic sites around the country, meaning roughly 130,000 pupils visited them last year. The trips have been linked to an increase in the number of students studying history or related courses in Scotland in the last five years.
Edinburgh Castle remains the most popular paid-for tourist attraction in Scotland with 1.3 million people passing through its gates last year. It was voted the top UK attraction for the second consecutive year at the recent British Travel Awards.