Now that I think about it, this means that there is a Union Soldier without a military marker, probably in Otoe County, Nebraska.
This is the Martin Foster who was in the 4th Iowa.

Source: "List of Pensioners on the Roll, January 1, 1883; giving the name of each pensioner, the cause for which pensioned, the post-office address, the rate of pension per month, and the date of original allowance, as called for by Senate Resolution of December 8, 1882." Vol. IV, pages 746-747.
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Otoe Co., NE; Military Pensioners, 1 January 1883
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Certif. No. Name of pensioner Post Office Addr. Cause for which pensioned Monthly rate Date of orig. allowance
177, 250 Foster, Martin Unadilla g.s.w. abd. 2 00 Oct., 1880