"Michigan National Guard Units, the 31st, 32nd, 33rd, 34th and 35th Michigan Infantry were deployed.Volunteers were added to the units during the war.A Naval Unit also served. The 35th did not leave the USA. More deaths resulted from disease than battle.
The names were extracted from: Title: Michigan Volunteers of '98. Published: Detroit, Michigan by G. F. Sterling & Co. in 1898.
6,893 named veterans served in Michigan Regiments Each person's name, place of residence at sign up, regiment and company are listed plus rank."
Looking at the database link of Names has this William L. Hampton that lived in Ovid, Clinton County, MI that was in the 35th Michigan Infantry Co. D.
There is a Wm L Hampton that filed for a pension based on SpAm War service which are included in the database titled "US,Civil War Pensions Index..." He filed in MI June 17, 1901 as a Invalid. There is also another Unit listed that he served in besides the 35th Co D...Co F, US Vol Inf 29th.
On Find a Grave is the burial of William L. Hampton b. 1864 d. 1945 has Military Marker with "Private, 29th US Vol Inf" engraved on it. Riverside Cemetery, Elsie, Clinton County MI.
1880 Census your Wm Hampton in living in Bay County MI but has birth place as England, parents James and Mary. There is another William Hampton b. 1865 IN, living in Clinton County MI. Also Wm L Hampton is still in Army in 1900 census stationed at the Philippine Islands. Has home town as Ovid, Clinton Co MI born Tampico, Indiana.
So no I do not think the Wm Hampton of the 35th Do D is "your" William Hampton.