What about "Free, white, male, 21 and a property owner" being required to vote?
While it may have later emerged that there were strong antislavery factions in the North, Northern states had slaves, too, and until there were numerous immigrants to exploit, those slaves were important to the northern economy, but not treated as "citizens".
http://www.uscis.gov/files/nativedocuments/Citizenship_2004.pdf
Ways of Becoming a Citizen
Citizenship by Birth
In general, citizenship is conferred upon a child automatically at birth. While there is no universal rule concerning citizenship and nationality, most nations follow the legal principles of jus soli or jus sanguinis, or a combination of the two.
Jus soli is the right of birthplace, i.e., citizenship is conferred at birth when a child is born within the borders of the nation. This principle dictates that persons born in a country automatically become citizens of that country, regardless of their parents’ citizenship or legal residence.
Jus sanguinis is the right of blood. In other words, citizenship is earned by inheriting the nationality of one’s parents. Under this principle, a child born abroad may derive citizenship from his or her parents, thus becoming a citizen of the parents’ country of citizenship. Alternatively, a child born in a country that follows the principle of jus sanguinis does not automatically become a citizen of that country unless the parents are citizens.
In practice, the citizenship laws of many countries follow a combination of both principles. For example, in the United States, in almost all cases, a child born within the borders of the country becomes a citizen, regardless of the parents’ nationality (jus soli). In addition, a child born abroad of U.S. citizen parents is also a United States citizen, with certain exceptions (jus sanguinis). The United Kingdom, on the other hand, requires at least one parent to be a citizen or settled in the United Kingdom for a child born in the country to be a citizen.
Legal Context of Dual Nationality
The Hague Convention of 1930 stated that the each nation is responsible for determining who may be a citizen or national of their country and declared that dual nationality, or dual citizenship, is undesirable.
Dual nationality may be acquired through a variety of means, depending on the citizenship and naturalization laws of the countries involved:211
1. Birth: A child born in a country that follows the principle of jus soli acquires the citizenship of that country by the fact of being born within that country. However, that child may also acquire the citizenship of his or her parent(s) if the parent(s) is a citizen of another country and that country follows the rule of jus sanguinis, by which a child derives citizenship through his or her parent(s).
2. Marriage: In certain countries, a person can automatically acquire the citizenship of his or her spouse upon marriage.
3. Naturalization: Some countries permit naturalization without renunciation of former citizenship. Similarly, some countries do not automatically revoke a person’s citizenship when another citizenship is acquired.
4. Treaty: Some countries have agreement with certain other countries permitting dual citizenship among their respective nationals.
5. Default: A person naturalized by another country without the approval of his or her country of origin may be considered to still be a citizen of the original country. This could happen, for example, in the case where the original country is not notified that another citizenship has been acquired and, thus, that individual continues to be recognized by the original country of citizenship. Further, in some countries, citizenship may never be lost, thus the acquisition of another citizenship results in the individual having dual citizenship.212
While some countries recognize dual nationality, others do not. One problem associated with possessing the citizenship of two countries is that there may be situations in which the obligations of a dual citizen are in conflict. An example of this is conflicting military obligations making it difficult or impossible for a dual national to fulfill the obligations of both countries.213 There also may be penalties for failure to meet certain obligations while absent from one country of nationality, or one country may not recognize the other nationality, therefore denying consular assistance from the foreign government.214
U.S. Policy
The current citizenship and immigration laws of the United States do not specifically address dual nationality. According to the State Department, “the U.S. Government recognizes that dual nationality exists but does not encourage it as a matter of policy because of the problems it may cause.”216 The State Department notes that problems may arise from
• claims of other countries on dual national U.S. citizens that may conflict with U.S. law;
• conflicts that arise from a dual national’s allegiance to both the United States and the foreign country;
• dual nationals are required to obey the laws of both countries, which may be in conflict; and
• each country having the right to enforce its laws, particularly when the dual national is in that country.
Further, U.S. Government efforts to assist its dual citizens abroad may be limited. In particular, the country where a dual national is located generally has a stronger claim to that person's allegiance.