Which article in the constitution gave a special status to Kashmir?

Article 370

Under Article 370 of the Indian Constitution, Jammu and Kashmir enjoyed a distinctive status. However, this unique status did not shield the region from challenges. Despite its special status, Jammu and Kashmir encountered a turbulent mix of violence, cross-border terrorism, and political instability. These internal and external factors had far-reaching consequences.

In June 2018, the President's rule was enforced after the BJP withdrew its support from the Mufti government. Subsequently, on 5 August 2019, Article 370 was abolished via the Jammu & Kashmir Reorganisation Act 2019, leading to the division of the state into two Union Territories: Jammu & Kashmir and Ladakh.
Jammu & Kashmir and Ladakh stand as living examples of a plural society within India. The regions exhibit diverse facets—be it religious, cultural, linguistic, ethnic, or tribal. These diversities also extend to political and developmental aspirations, which the recent Act sought to address and fulfill.