Exhibit 31.2

Certification of Principal Financial Officer

I, Kathleen M. Jepson, certify that:

| 1)     | I have reviewed this quarterly report on Form 10-QSB   of Horizon Bancorporation, Inc,.;                                                                                                                                                                                                                                               |
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| 2)     | Based on my knowledge, this quarterly report does   not contain any untrue statement of a material fact or omit to state a   material fact necessary to make the statements made, in light of the circumstances   under which such statements were made, not misleading with respect to the   period covered by this quarterly report; |
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| 3)     | Based on my knowledge, the financial statements, and   other financial information included in this quarterly report, fairly present   in all material respects the financial condition, results of operations and   cash flows of the registrant as of, and for, the periods presented in this   quarterly report;                    |
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| 4)     | The registrant’s other certifying officers and I are   responsible for establishing and maintaining disclosure controls and   procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))   [Intentionally Omitted] for the registrant and we have:                                                                     |
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|   | a)                                                                                                                                                                                                                                                                                                                                     | designed such disclosure controls and procedures to   ensure that material information relating to the registrant, including its   consolidated subsidiaries, is made known to us by others within those   entities, particularly during the period in which this quarterly report is   being prepared; |
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|   | b)                                                                                                                                                                                                                                                                                                                                     | [Intentionally Omitted]; |
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|   | c)                                                                                                                                                                                                                                                                                                                                     | evaluated the effectiveness of the registrant’s   disclosure controls and procedures and presented in this report our   conclusions about the effectiveness of the disclosure controls and procedures   as of the end of the period covered by this report based on such evaluation;   and |
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|   | d)                                                                                                                                                                                                                                                                                                                                     | disclosed in this quarterly report any change in the   registrant’s internal control over financial reporting that occurred during   the registrant’s most recent fiscal quarter that has materially affected, or   is reasonably likely to materially affect, the registrant’s internal control   over financial reporting; |
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| 5)     | The registrant’s other certifying officers and I   have disclosed, based on our most recent evaluation, to the registrant’s   auditors and the audit committee of registrant’s board of directors (or   persons performing the equivalent function):                                                                    |
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|   | a)                                                                                                                                                                                                                                                                                                                                     | all significant deficiencies and material weakness   in the design or operation of internal control over financial reporting which   are reasonably likely to adversely affect the registrant’s ability to record,   process, summarize and report financial information; and |
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|   | b)                                                                                                                                                                                                                                                                                                                                     | any fraud, whether or not material, that involves   management or other employees who have a significant role in the registrant’s   internal control over financial reporting. |

Date: August 14, 2006

| /s/ Kathleen M. Jepson                     |   |
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| Vice President and Chief Financial Officer |   |