Tuhia he tohutoro mō tēnei wāhanga - I whānau a Granger ki Zanesville, Ohio. I puta ia i te United States Military Academy, i te 28 o nga tau o te tau 1838. I riro a Granger hei rangatira tuatahi o te ope taua i te tau 1839. I mahi ia hei rangatira i te Pakanga Seminole
, a ko ia te kaiawhina kaiako o te rautaki i West Point i te 1843/44. I te Pakanga o Mexico-Amerika, i whakatairangahia a Granger ki te rangatira i te Mahuru 8, 1847. I te mutunga o te pakanga, ka tukuna ia ki ngā pou maha i te rohe o Texas.