Found the following article online, use it to answer the question: What are the names of the state that was formed when its last merger was completed on May 15 1948?  The bulk of the larger states, and some groups of small states, were integrated through a different, four-step process. The first step in this process was to convince groups of large states to combine to form a "princely union" through the execution by their rulers of Covenants of Merger. Under the Covenants of Merger, all rulers lost their ruling powers, save one who became the Rajpramukh of the new union. The other rulers were associated with two bodies—the council of rulers, whose members were the rulers of salute states, and a presidium, one or more of whose members were elected by the rulers of non-salute states, with the rest elected by the council. The Rajpramukh and his deputy Uprajpramukh were chosen by the council from among the members of the presidium. The Covenants made provision for the creation of a constituent assembly for the new union which would be charged with framing its constitution. In return for agreeing to the extinction of their states as discrete entities, the rulers were given a privy purse and guarantees similar to those provided under the Merger Agreements.Through this process, Patel obtained the unification of 222 states in the Kathiawar peninsula of his native Gujarat into the princely union of Saurashtra in January 1948, with six more states joining the union the following year. Madhya Bharat emerged on 28 May 1948 from a union of Gwalior, Indore and eighteen smaller states. In Punjab, the Patiala and East Punjab States Union was formed on 15 July 1948 from Patiala, Kapurthala, Jind, Nabha, Faridkot, Malerkotla, Nalargarh, and Kalsia. The United State of Rajasthan was formed as the result of a series of mergers, the last of which was completed on 15 May 1949. Travancore and Cochin were merged in the middle of 1949 to form the princely union of Travancore-Cochin. The only princely states which signed neither Covenants of Merger nor Merger Agreements were Kashmir, Mysore and Hyderabad.
The answer to this question is:
The United State of Rajasthan