The Brahmo Samaj, a prominent reform movement in India, was founded in 1828 in Kolkata (formerly known as Calcutta). It was established by Raja Ram Mohan Roy, a social reformer and intellectual, with the help of his close friend and associate, Dwarkanath Tagore.

At the time of its founding, India was under British colonial rule and was experiencing social, religious, and political turmoil. The traditional Hindu society was plagued by issues such as caste discrimination, child marriage, and the practice of Sati (burning of widows on their husband's funeral pyre). In addition, the influence of Western education and ideas was growing, leading to a clash between traditional beliefs and modernity.

In this context, Raja Ram Mohan Roy sought to create a society that rejected the rigid and oppressive aspects of Hinduism and embraced a more rational and ethical approach to religion. He was deeply influenced by the ideas of the Enlightenment and the Unitarian Church, which emphasized the oneness of God and the importance of reason and morality.

Initially, the Brahmo Samaj was a small group of like-minded individuals who met in Roy's house to discuss and debate various social and religious issues. However, as the movement gained popularity, it evolved into a formal organization with a defined set of principles and practices.

The first major event of the Brahmo Samaj was the publication of its manifesto, the 'Tattvabodhini Patrika' (The Journal of the Search for Truth), in 1839. This journal served as a platform for the Samaj's ideas and beliefs, which included the rejection of idol worship, caste distinctions, and the authority of the Vedas.

In 1843, the Brahmo Samaj took a significant step towards reform by conducting the first inter-caste marriage in India between a Brahmin and a non-Brahmin. This was a bold move that challenged the deeply ingrained caste system and paved the way for social equality and inclusivity.

Under the leadership of prominent figures such as Debendranath Tagore (son of Dwarkanath Tagore) and Keshub Chandra Sen, the Brahmo Samaj continued to grow and spread its message of social and religious reform throughout India. It also played a crucial role in the Indian Independence movement, with many of its members actively participating in the fight against British colonialism.

In conclusion, the Brahmo Samaj was founded in 1828 in Kolkata as a response to the social, religious, and political challenges of the time. It aimed to promote monotheism, rationality, and social equality, and its impact on Indian society and culture continues to be felt even today.