The 138th was now an active unit as of June 6th 1863.The regiment was placed in Elliott's Brigade, which was under General French's 3rd Division II Corps. The unit mostly picketed and patrolled the area. However, the 138th was not there long. One July 1st 1863 Harper's Ferry was evacuated. Ammunition stores that could not be moved to Washington were destroyed. Elliott’s Brigade would be one of the units to accompany the munitions to Washington DC. After successfully safeguarding the ammunition to Washington, the brigade was transported by rail to Frederick where it rejoined the division. General French would then be replaced with Colonel Elliott as commander of the division. On the 16th the division will cross the river at Harper's Ferry and pursue the retreating Army of Northern Virginia.