I am not related to this William Shannon. I just happened upon an interesting advertisement in an issue of The Schenectady Cabinet [newspaper] from 1835 and saved it. Maybe this William Shannon is "yours." The source info and text of the advertisement is as follows:

The Schenectady Cabinet [newspaper], Schenectady, New York. Wednesday, September 9, 1835

From: FultonHistory.com
TinyURL link: http://tinyurl.com/p33spzg

RANAWAY from the subscriber on the 2d. inst. WILLIAM SHANNON, an indented apprentice to the Harness Making business, aged twenty years and seven months, according to his indentures – although his father now says he is twenty-one. Said William may be known by his sullen, ugly disposition. I suppose this to be natural, as he has made it manifest since he has been with me, particularly of late. This is to forbid all persons trusting or harboring him under penalty of the law. I hope no person will wish to injure me so much as to bring him back. – Schenectady, Sept. 8, 1835. JOSEPH LYON.

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An image of the newspaper advertisement is attached.

Best wishes.