According to descendant Glenna Bishop, the 1880 census shows Martin homeless at age 17.
1880 Census - Fayette County, Pennsylvania
Springhill TWP - 26 June 1880

  146
  Stewart, Franklin  W M 35      Selling Dry Goods  Penn Penn Va
  Margrett           W F 35 Wife Keeping House      Penn Md   Penn
  Jesse              W M 15 Son  At Home            Penn Penn Penn
  David              W M 12 Son                     Penn Penn Penn
  Laura              W F 10 Dau                     Penn Penn Penn
  Oarin              W M  7 Son                     Penn Penn Penn
  Francis M.         W M  5 Son                     Penn Penn Penn
  Sarah              W F  2 Dau                     Penn Penn Penn
  Dunham, Martin     W M 17 Boarder                 Penn Penn Penn

1900 Census - Fayette County, PA, Georges TWP

246 253
Dunham, Mark   Head W M May 1863 37 M 1 Penn Penn Penn Farmer
    Emma M     Wife W F Jan 1881 19 M 1 0 0 Penn Penn Penn

Bernard Mayhle states from personal knowledge that his name was Martin, and that the census taker
must have made a mistake.

1910 Census - Fayette County, PA - Georges TWP

  132 150
  Dunham, Martin   Head M W 46 M1 10      Penn Penn Penn
  Emma             Wife F W 29 M1 10 7 7  Penn Penn Penn
  Lizzie C.        Dau  F W  9 S          Penn Penn Penn
  Earl M.          Son  M W  8 S          Penn Penn Penn
  Anna R.          Dau  F W  7 S          Penn Penn Penn
  William R.       Son  M W  5 S          Penn Penn Penn
  Joseph R.        Son  M W  4 S          Penn Penn Penn
  Olive M.         Dau  F W  2 S          Penn Penn Penn
  Paul E.          Son  M W  1 S          Penn Penn Penn
  [illegible]      ???  M W 19 S          Penn Penn Penn

1920 Census - Fayette County, PA - Georges TWP
2 Feb 1920

  175
  Dunham, Martin  Head M W 56 M W.Va W.Va W.Va
  Emma            Wife F W 39 M Penn Penn Penn
  Catherine E.    Dau  F W 19 S Penn Penn Penn
  Earl M.         Son  M W 18 S Penn Penn Penn
  Annie R.        Dau  F W 16 S Penn Penn Penn
  William R.      Son  M W 15 S Penn Penn Penn
  Joseph R.       Son  M W 14 S Penn Penn Penn
  Olive M.        Dau  F W 12 S Penn Penn Penn
  Paul E.         Son  M W 11 S Penn Penn Penn
  Charles H.      Son  M W  9 S Penn Penn Penn
  John C.         Son  M W  7 S Penn Penn Penn
  Ellenor P.      Dau  F W  5 S Penn Penn Penn
  Margret B.      Dau  F W  4 S Penn Penn Penn
  Harry S.        Son  M W  2 S Penn Penn Penn
  Franklin V.     Son  M W 8/12  S Penn Penn Penn

  176
  Miller, Philip G. Head M W 70 Wd Penn Penn Penn
  Swanager, Catherine Housekeeper F W 56 Wd W.Va  W.Va  W.Va 

From Vance Funeral Home records (974.884 V3m):

Nellie Viola Dunham
9-19-1923 9-29-1924
Father: Martin  Mother: Emma Miller
Miller Sisler Cem. Haydentown, Pa.

Obituary of Nellie Viola Dunham (submitted by Kristi Kennison):

Nellie Viola Dunham, aged 1 year, 10 days, died on Monday morning, between 5:30 and 6 o'clock, at the
home of her parents, Pr. and Mrs. Martin Dunham, near White House.  She died of summer complaint. 
She is survived by her parents and the following sisters and brothers: Mrs. A. J. Cummings, of Shady
Side, Pa.; Mrs. Guy Quinn and Earl Dunham, of Smithfield; William Ray, Joseph Roy, Olive Marie, Paul
Edison, Charles Herbert, J. C., Eleanor Pearl, Margaret Belle, Harry Samuel, Franklin V., and Edythe
Irene all at home.  She is also survived by three nieces and two nephews.  Funeral services will be
held Wednesday at 2 o'clock.  Interment in the Sister's Grave Yard.

1930 Census - Fayette COunty, Pennsylvania
Georges TWP - April 22, 1930

  Brownfield Hollow in Mountain
  322 322
  Dunham, Martin    Head M W 66 M 36 Penn Penn Penn Farmer
  Emma              Wife F W 49 M 18 Penn Penn Penn
  Paul              Son  M W 21 S Penn Penn Penn
  Herbert           Son  M W 19 S Penn Penn Penn
  Clarence          Son  M W 17 S Penn Penn Penn
  Eleanore P.       Dau  F W 15 S Penn Penn Penn
  Margaret B.       Dau  F W 14 S Penn Penn Penn
  Harry S.          Son  M W 13 S Penn Penn Penn
  Franklin V.       Son  M W 10 S Penn Penn Penn
  Edith             Dau  F W  9 S Penn Penn Penn
  Pearl             Dau  F W  7 S Penn Penn Penn