There are 16 William Lassiter who served in the Confederate Army as found in the Historical Data Systems records. Here are two who enlisted in Northampton County.

William B. Lassiter
Residence Northampton County NC; 26 years old.
Enlisted on 7/6/1861 at Northampton County, NC as a Private.
On 7/6/1861 he mustered into "H" Co. NC 2nd Cavalry
He was discharged on 2/18/1864
He was listed as:
* On rolls 10/15/1863 (place not stated) (Estimated day)

……………

William H. Lassiter
Residence was not listed;
Enlisted on 10/1/1862 at Northampton County, NC as a Private.
On 10/1/1862 he mustered into "A" Co. NC 12th Battn Cavalry
He was transferred out on 4/30/1864
(Estimated day of transfer)
On 4/30/1864 he mustered into "E" Co. VA 10th Cavalry
(date and method of discharge not given)
He was listed as:
* AWOL 7/15/1864 (place not stated) (Estimated day. AWOL through 08/64)

Sources used by Historical Data Systems, Inc.:
- North Carolina Troops 1861-65, A Roster