Adam is found in the Port Washington cemetery. This cemetery is located in the town on the west side.Looking at the MSN Map it would appear to be at the end of Glasgow Road, S.W.His second wife and their son Frank W. is there too.I can see this is correct by comparison of the 1880 and 1900 census record.Benjamin appears in both (as well as Adam).
Dates: Adam Ross 1853-1903 Eliza J. 1858-1912 Frank W. 1889-1911
From the wedding book, Adam married Eliza Jane Jones on 19 May 1887.
There are a few other markers that appear to be related in the Port Washington Cemetery:
George Ross s/A. & M. d 21 Feb 1877 4m6d Caroline Ross d/A. & M. d 15 Jan 1880 16d Benjamin 1875-1940 (Next to Henry and Margaret Schug)
Henry W. Schug 16 Jul 1827-19 Nov 1902 Margaret 15 Dec 1820-13 Oct 1902 Henry, Jr. 1862-1931
Adam's father/step mother/brother (see 1870 census): Benjamin 1828-1881 (Dec 19 from death records) Clarissa 1841-1899 Wilbert P. 1868-1891
Benjamin Harvey Ross s/B. & C. 15 Dec 1853 1y (Gnadenhutten Cem.) Caroline Ross w/ Benj. 10 Jun 1828-20 Dec 1864
Marriages: Benjamin Ross + Caroline Klaine 20 Jul 1851 Benjamin Ross + Clarissa Davis 2 Apr 1866