Important tasks for the First Congress of the U.S. were establishing the requirements for the first census of the country and for becoming a citizen by naturalization. 
Anyone who has studied any American history knows that slavery existed at the adoption of the U.S. Constitution in 1788 and that the Constitution’s original Article I, Section 2 apportioned representatives in the House of Representatives “according to their respective Numbers, which shall be determined by adding to the number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons [i.e., slaves].” (Emphasis added.)
Therefore, it should not be surprising that the very First Congress of the U.S. enacted a statute for the first U.S. census and a statute establishing requirements for becoming a naturalized U.S. citizen, both of which distinguished between “white” individuals and “slaves.” Nevertheless, it was still startling for me to discover these two statutes and the subsequent history of these aspects of U.S. law.
The First U.S. Census
On March 1, 1790, the First Congress enacted a statute that established the following categories for the first enumeration or census: “Free white males of sixteen years and upwards, including heads of families; Free white males under sixteen years; Free white females, including heads of families; All other free persons; and Slaves.” (Emphasis added.) It also called for identifying an individual’s occupation.
These provisions were not controversial. There, however, was controversy, according to Fegus Bordewich, over whether the first census “was too ambitious, too detailed, and subdivided the population into [occupational] ‘classes too minute’” and was too invasive of privacy. (P. 196)
The First Naturalization Statute
On January 8, 1790, President George Washington delivered the first State of the Union address, in which he said, “Various considerations also render it expedient that the terms on which foreigners may be admitted to the rights of citizens should be speedily ascertained by a uniform rule of naturalization.”(P. 180) 
Thereafter the members of the First Congress debated whether an oath of allegiance should suffice, whether there should be a residence requirement, whether there should be a national or a state-by-state requirement and whether foreign seamen could easily become citizens. The answer to these fears apparently was provided by Virginia’s Representative John Page, a large slave owner: “’It is nothing to us whether Jews, or Roman Catholics, settle amongst us; whether subjects of kings or citizens of free states wish to reside in the [U.S.], they will find it their interest to be good citizens; and neither their religious or political opinions can injure us, if we have good laws, well executed.’” (Pp. 196-97)
On March 26, 1790, the First Congress enacted a statute that limited naturalization to an “alien, being a “free white person.”(Emphasis added.) Although the statute did not define that term, it clearly excluded Native Americans, indentured servants, slaves, free blacks and Asians from this method of obtaining U.S. citizenship. Other requirements were being a “resident” for one year of a state, possessing “good character,” and having taken “an oath or affirmation . . . to support the constitution of the [U.S.].” 
As discussed in another post, the “white” racial category (with subsequent additions of other racial categories) for naturalization remained in U.S. statutes until 1952 when Congress enacted the McCarran-Walter Act, 60 Stat. 163, 239 (1952), which states in section 311, “The right of a person to become a naturalized citizen of the United States shall not be denied or abridged because of race or sex or because such person is married.” 
 See generally The U.S. First Congress: Overview, 1789-1791, dwkcommentaries.com (Feb. 15, 2017); Fergus Bordewich, The First Congress: How James Madison, George Washington, and a Group of Extraordinary Men Invented the Government (Simon & Schuster, New York, 2016)[the above text of this post cites to to specific pages of this book].
 The above provision of the original Constitution was deleted by Section 2 of the Fourteenth Amendment thereto, which was adopted after the Civil War in 1868 and which states: “Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed.”
 An Act providing for the enumeration of the Inhabitants of the United States, 1 Stat. 101 (1790), U.S. Constitution. The “white” category has been used in every decennial census through 2010 while “slave” was used through 1840.
 President Washington, State of the Union Address, (Jan. 8, 1790), presidency.ucsb.edu/was/?pid=29431 , http:www.
 An Act to establish an uniform Rule of Naturalization,” 1 Stat. 103 (1790),
 Long History of Racism in U.S. Laws Regarding United States Citizenship, dwkcommentaries.com (June 24, 2016).