James St Clair-Erskine was born on 6 Feb 1762, the son of Lieutenant-General Sir Henry Erskine, 5th Bt. His mother was Janet Wedderburn, daughter of Lord Chesterhall, a Lord of Session. She was sister to Alexander Wedderburn, 1st Earl of Rosslyn. James was educated at Edinburgh High School and at Eton. He was a politician as well as a soldier, elected as a Whig MP in 1782 supporting Charles James Fox, but changed to the Tories around 1805 when he entered the House of Lords as the 2nd Earl of Rosslyn. He adopted the name St Clair-Erskine in 1789 when he inherited the Rosslyn and Dysart estates from his cousin, James Paterson St Clair.
His career as an army officer started with the 2nd Dragoons in 1778 but within 4 years he had a staff position as ADC in Ireland. In 1793 he was Adjutant-General of the army that besieged Toulon and invaded Corsica. In 1807 he commanded a Division as a lieutenant-general at the Battle of Copenhagen. He was in Lisbon in 1806 to help secure the appointment of Sir Arthur Wellesley as Commander-in-Chief in the Peninsula.
He was Colonel of the 9th Light Dragoons (Lancers) for 36 years, from August 1801 until his death on 18 January 1837. The Earl was married in 1790 to Harriet Elizabeth, daughter of the Hon Edward Bouverie. She died in 1810. They had a daughter, Lady Janet, and two sons, James and Henry. Their son, James Alexander, succeeded to the title as 3rd Earl of Rosslyn, and was commanding officer of the 9th Lancers from 1828 to 1842.
1765 Succeeded his father to become 6th Baronet
1778 Lieutenant in the 2nd Dragoons
1780 Captain in 19th Light Dragoons
1782 ADC to Lord Lieutenant of Ireland
1782 MP for Castle Rising
1783 Appointed Adjutant-General
1784 MP for Morpeth
1789 Changed his name to be Sir James St Clair-Erskine 6th Bt
1790 Married to Harriet Elizabeth Bouverie
1792 Lieutenant-Colonel in the 12th Light Dragoons
1793 Siege of Toulon
1794 Invasion of Corsica
1795 Promoted to colonel
1795 ADC to King George III
1796 MP for Dysart Burghs in Fife
1796 Promoted to Brigadier General in Portugal
1798 Promoted to Major-General
1798 Appointed Commander-in-Chief in the Mediterranean
1801 Colonel of the 9th Lancers
1805 Succeeded his uncle as Earl of Rosslyn
1805 Promoted to Lieutenant General
1806 Special mission to Lisbon
1807 Battle of Copenhagen
1809 Walcheren Expedition
1814 Promoted to General
1820 Knight Grand Cross Order of the Bath (GCB)
1828 Lord Lieutenant of Fifeshire
1829 Member of the Cabinet as Lord Privy Seal
1829 On the Privy Council
1837 Died at the age of 74 on 18 January.
