An option is to put an "A" chord and then a "D" chord in the First line as in:
D A D Bm I was born on this mountain a long time ago
Or leave it as it is. This option can apply to the first Line of every verse, as you like.
INTRO D Bm D Em G D
1st VERSE
D Bm I was born on this mountain a long time ago D Em G Bm Before they knocked down the timber and strip-mined the coal D Bm When you rose in the mornin' before it was light D Em G Bm A To go down in the dark hole and come back up at night
CHORUS:
D Bm I was born on this mountain, this mountain's my home D Em G A And she holds me and keeps me from worry and woe D Bm