Prior to 1906, virtually any court could award citizenship. After 1906, awarding citizenship was restricted to certain higher level courts and more information was required. Attaining citizenship was a multi-step process.
After being in the United States for a period of time (at least two years), the immigrant was eligible to apply for so-called first papers, which was a declaration of intention to seek U.S. citizenship.
First Papers of Julius Skvarenina
Following another period of time (at least three years), the individual could then petition for citizenship. In addition to being in the U.S. for at least five years, the individual had to have been in one state for the last year. After 1906, it was necessary to obtain a certificate of arrival from the port of entry to the U.S.
Certificate of Arrival for Julius Skvarenina
The applicant filled out the petition with the required information and had two witnesses provide affadavits.
Petition and affidavits for Julius Skvarenina
Eventually the court either approved or disapproved the request. In Julius' case, he applied in November, 1920 and was approved in April, 1921. He completed the oath of allegiance and the court admitted him. When approved, the individual was provided a certificate of citizenship. A second copy of the certificate was sent to Washington DC.
Oath of allegiance and court order
Since Julius was married, his wife Anna became a citizen with him. This rule changed in 1922 (for more information see the National Archive link below).
The Immigration and Naturalization Service (INS) claims to have all certificates on file from 1906. Information is at the following website.
http://www.ins.gov/graphics/aboutins/history/NatzRec/NATREC.htm
The National Archives and its regional offices also maintain microfilm copies of many citizenship records, as well as some indexes. The court papers linked on this page were obtained from the Chicago office for a small fee ($10.00). The following link has a lot of information about the citizenship process: