Hallelujah for former Clinton County Circuit Clerk, Jeff Luebbers! He has indexed the Clinton County Naturalization records in the 18 Clinton County books and is willing to share those indexed names with us.
This index is a compilation of almost 3,000 Naturalization records available at the Clinton County Courthouse. There might be something precious on the document, like the name of the village the person came from, or a person's signature, or a couple relatives' names, etc. Or, there might be absolutely no new information at all. But anything at all is a great find, and something irreplaceable.
If you'd like a copy of any of these records, click on the "Click Here for the Fee Schedule" on the Circuit Clerk's web page.
Copies can also be ordered from IRAD.
Microfilmed copies can be ordered and viewed from any Family History Center of the Mormon Church (Jesus Christ of the Later Day Saints). There is a copy at the O'Fallon, IL FHC for your use.
The story of how people became Naturalized is free at Ancestry.com Naturalization Records
As Ancestry.com says, people could have filed their papers at any county or federal courthouse and may have filed their first papers at one location, their second papers in another locations and their final papers in a third location. Stories say some Clinton County people went to Belleville and East St. Louis, and there were probably those who went to St. Louis, Greenville and Centralia, too.