The history of Ajmer sublimes in 7 century A.D, when scion from Macavati of Chauhan dynasty, Ajaipal established himself at Ajmer and erected the fort of Tarragarh(present name). His successor Dola Rae, lost Ajmer to Islamic Invasions, to be recovered by Manik Rae. Rao Beelundeo defended Ajmer against Mahmud of Ghazni and Ajmer continued to be ruled by Chauhan dynasty, in spite of repeated invasions by Turkic Muslim armies from Central Asia across the north of India.
Prithviraj Chauhan, also known as Rai Pithora succeeded to the throne in 1178 CE at the age of 13. Chauhan defeated Muhammad Ghori in the First Battle of Tarain in 1191 but was defeated, captured at the Second Battle of Tarain (1192).
Khawaja Muinuddin Chishti famous as Garib Nawaz, visited Ajmer during reign of Prthvi Raj Chauhan and established the Chishti Order of Sufism in the Indian subcontinent.
Even after Ajmer was conquered by Muhammad of Ghor, founder of the Delhi Sultanate, in 1193. The Chauhan rulers were able to gain autonomy upon the payment of a heavy tribute to him. Ajmer regained independence under the ruler of Mewar in 1365. Shortly there began contest between Maharajas of Mewar and Marwar for control of Ajmer, until 1532 when it was conquered by the Marwar.
In 1553, the state was controlled by the Hindu Emperor Hem Chandra Vikramaditya (Hemu). In 1556, Hemu was defeated and killed in the Second Battle of Panipat and control of Ajmer passed to the Mughal emperor Akbar in 1559. It was in Ajmer that Sir Thomas Roe, as ambassador of King James I of England, had his audience with Emperor Jahangir on 19th January 1616 A.D. which laid the stepping stone of the British Raj in India through the charter of free trading granted to the East India Company by the Emperor.
In 1627 A.D, it was in Ajmer that Shah Jahan, on the death of Jahangir, proclaimed himself Emperor of India while returning from Udaipur and proceeding to Delhi. And after a furious battle on 11th, 12th and 13th of March 1659 A.D, it was in Ajmer again that a beginning of the decline of Moghul Empire was made with the victory of Aurangzeb against his brother Dara Shikoh .
In the early 1700s century, control passed to the Marathas.
In 1818 Ajmer became part of the Province of Ajmer-Marwar in the colonial British Raj when British forced the Marathas to cede the city for 50,000 rupees. It consisted of the districts of Ajmer and Merwara, and were physically separated by the territory of the Rajputana Agency. Ajmer-Marwar was directly administered by the British Raj, by a commissioner who was subordinate to the Governor-General’s agent for Rajputana.
Ajmer-Marwar remained a province of India until 1950, when it became the Ajmer State. Ajmer state became part of Rajasthan state on 1 November 1956