In regard to Fort Mahone Aka Battery 29 Petersburg VA April 1865
Site as it is alleged to have appeared in 1892 {Frassanito indicates Picket Post was CS not US}
http://books.google.com/books?id=eml9U2RZArQC&pg=PA257&dq=Rhode+Island+Regiment+at+Fort+Mahone&hl=en&sa=X&ei=WUBRT9LLLqnb0QHI1NTVDQ&ved=0CDAQ6AEwAA#v=onepage&q&f=false

Site was later covered by monument to Union Army 9th Corps/3rd Division
http://books.google.com/books?id=roovAAAAYAAJ&pg=PA65&dq=PA+monument+at+site+of++Fort+Mahone&hl=en&sa=X&ei=DEFRT9LjCMP10gGs0IThDQ&ved=0CDsQ6AEwAA#v=onepage&q=PA%20monument%20at%20site%20of%20%20Fort%20Mahone&f=false