We proceed, therefore, to inquire whether the facts relied on by the plaintiff entitled him to his freedom. The case, as he himself states it, on the record brought here by his writ of error, is this: The plaintiff was a negro slave, belonging to Dr. Emerson, who was a surgeon in the army of the United States. In the year 1834, he took the plaintiff from the State of Missouri to the military post at Rock Island, in the State of Illinois, and held him there as a slave until the month of April or May, 1836. At the time last mentioned, said Dr. Emerson removed the plaintiff from said military post at Rock Island to the military post at Fort Snelling, situate on the west bank of the Mississippi river, in the Territory known as Upper Louisiana, acquired by the United States of France, and situate north of the latitude of thirty-six degrees thirty minutes north, and north of the State of Missouri. Said Dr. Emerson held the plaintiff in slavery at said Fort Snelling, from said last-mentioned date until the year 1838. In the year 1835, Harriet, who is named in the second count of the plaintiff's declaration, was the negro slave of Major Taliaferro, who belonged to the army of the United States. In that year, 1835, said Major Taliaferro took said Harriet to said Fort Snelling, a military post, situated as hereinbefore stated, and kept her there as a slave until the year 1836, and then sold and delivered her as a slave, at said Fort Snelling, unto the said Dr. Emerson hereinbefore named. Said Dr. Emerson held said Harriet in slavery at said Fort Snelling until the year 1838. In the year 1836, the plaintiff and Harriet intermarried, at Fort Snelling, with the consent of Dr. Emerson, who then claimed to be their master and owner. Eliza and Lizzie, named in the third count of the plaintiff's declaration, are the fruit of that marriage. Eliza is about fourteen years old, and was born on board the steamboat Gipsey, north of the north line of the State of Missouri, and upon the river Mississippi. Lizzie is about seven years old, and was born in the State of Missouri, at the military post called Jefferson Barracks. In the year 1838, said Dr. Emerson removed the plaintiff and said Harriet, and their said daughter Eliza, from said Fort Snelling to the State of Missouri, where they have ever since resided. Before the commencement of this suit, said Dr. Emerson sold and conveyed the plaintiff, and Harriet, Eliza, and Lizzie, to the defendant, as slaves, and the defendant has ever since claimed to hold them, and each of them, as slaves. In considering this part of the controversy, two questions arise: 1. Was he, together with his family, free in Missouri by reason of the stay in the territory of the United States hereinbefore mentioned? And 2. If they were not, is Scott himself free by reason of his removal to Rock Island, in the State of Illinois, as stated in the above admissions? We proceed to examine the first question.