Gardner published the :
Missouri Citizen (City of Mexico, Audrain County, Mo.) 1863-186?
Dates of Publication:1863-186?
Created / Published:City of Mexico, Audrain County, Mo. : O.A.A. Gardner
Notes

- Weekly
- Description based on: Vol. 1, no. 13 (June 16, 1863).

Library of Congress Control Number
sn93059215
OCLC Number
27736696

And then his second attempt:

Feb 1865
COLUMBIA — Capt. Hugh Bradley, recently named local provost marshal for Boone and Howard counties, asked for stationery and help with an investigation from Lt. Horace Sayre, the provost marshal at Mexico.

Bradley asked Sayre to obtain an affidavit from O.A.A. Gardner, former provost marshal and publisher of the Mexico Beacon. Gardner was making his second attempt at publishing a newspaper in Mexico after purchasing the presses and offices of the Mexico Ledger from William Hunter.

Bradley wanted a statement from Gardner about the loyalty of Middleton Singleton, a farmer who lived near Centralia. Singleton and his family were to be banished, but his friends claimed he had been loyal since taking the oath of allegiance. Singleton helped form a company of men for the rebel Missouri State Guard in 1861.

Aug 1863
MEXICO — The Mexico Citizen newspaper lashed out at radical critics who had accused Editor O.A.A. Gardner of abandoning the cause of emancipation by endorsing the gradual plan approved by the State Convention.
“In a word, must all who receive the ordinance would favor be kicked out of the union church — excommunicated, we might also add exterminated?” the newspaper asked in an editorial. “It seems that such is the opinion of a certain class of men in this state, who have always been on a rampage so far as the question of slavery is concerned.”
The editorial is preserved by being reprinted in other newspapers. Almost all editions of the Citizen are lost.

Bits and piece's of the Missouri Citizen: https://audrain.mogenweb.org/1863citizen.htm