During the negotiation of the Dominican Republic's annexation to the US, President Grant was fairly insistent that the Dominican Republic be made a state rather than a territory.
Actually the proposed treaty provided explicitly for admission as a territory, with the possibility of
eventual statehood:
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Treaty celebrated between the United States of America and the Dominican Republic, for the incorporation of the second with the first.
The people of the Dominican Republic having, through their government, expressed their desire to be incorporated into the.United States as one of the
Territories [my emphasis--DT] thereof, in order to provide more effectually for their security and prosperity; and the United States being desirous of meeting the wishes of the people and government of that republic, the high contracting parties have determined to accomplish by treaty an object so important to their mutual and permanent welfare.
For this purpose the President of the United States has given full powers to Mr. Raymond H. Perry, United States commercial agent in the city of Santo Domingo, in the Dominican Republic, and the Presi dent of the Dominican Republic has given full powers to Mr. Manuel Maria Gautier, secretary of state for foreign affairs of the said Dominican Republic; and the said plenipotentiaries, after having coinmnnicated to each other their respective full powers, found in good and due form, have agreed upon and concluded the following articles:
Article I.
The Dominican Republic, acting subject to the wishes of its people, to be expressed in the shortest possible time, renounces all rights of sovereignty as an independent sovereign nation, and cedes these rights to the United States to be incorporated by them as an integral portion of the Union, subject to the same constitutional provisions as their other
Territories. [my emphasis--DT] It also cedes to the United States the absolute fee and property in all the custom-houses, fortifications, barracks, ports, harbors, navy and navy yards, magazines, arms, armaments, and accouterments, archives, and public documents of the said Dominican Republic, of which a schedule is annexed to this treaty; public lands and other property not specified excepted. *
Article II.
The citizens of the Dominican Republic shall be incorporated into the United States as citizens thereof, inhabiting one of its Territories, and shall be maintained and protected in the free enjoyment of their liberty and property as such citizens,
and may be admitted into the Union as a State, upon such terms and conditions and at such time as Congress shall provide by law. [my emphasis--DT]
https://books.google.com/books?id=aFP4UFhVv_wC&pg=PA98
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If the votes were not there for admission as a territory (either by treaty or joint resolution) they would certainly not be there for immediate admission as a state. It must be said, though, that the Dominicans under the treaty would fare better than the Puerto Ricans later would, in that they would immediately get US citizenship. Given racial prejudice, it would be hard to admit it as a state for a long time, yet maybe a Republican Congress would do so to get some safe new votes in Congress and the Electoral College.