The largest Princely state by area at the time of partition was Kashmir.
Out of 562 princely states during 1947, 13 princely states decided to join Pakistan.
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These 13 princely states are:
Bahawalpur: On 3 October 1947, the Nawab of Bahawalpur, Sadeq Mohammad Khan V, acceded his state to Pakistan, becoming the first ruler to do so successfully.
Khairpur: The state of Khairpur acceded to Pakistan on 3 October 1947.
Chitral: The Mehtar of Chitral, Muzaffar-ul-Mulk, stated his intention to accede to Pakistan on 15 August 1947. On 28 July 1969, President Yahya Khan announced the full integration