This his how I used to do it when the Kingston Trio were the folk group. Yes, I'm that old:

(E) One hundred and (D) eighty were (E)challanged by (D)Travis to (E) die. (*) (E)
By the line that he (D) drew with his (E)Sword when the (D) battle was (E) nigh. (*) (E)
The(A) man who would fight to the (E) death cross over, but (D) him that would live better (E) fly.
And over his (D) line walked a (E)hundred and (D) seventy (E} nine.(*) (E)

(A) hiii-yup, Santa Anna, we're killin' your soldiers be- (E)low, so the (D) rest of Texas will(E)know, and re- (B7) member the (E) Alamo, Re- (D) member the (E) Alamo(*) (E).

(*) means: Slide the first-position E up one fret, still leaving the the two E's and the B open, and play the whole six strings, and to hell with the dissonances.

Peter