Welcome to CornerStone Staffing, one of the leading staffing agencies in Richardson, TX. Best in Staffing Services. Best in Career Placement. The Best Choice for You! CornerStone Staffing – Richardson is located is located off US-75 / North Central Expressway and the President George Bush Turnpike near the new State Farm Insurance – CityLine campus. The Richardson staffing team of experienced recruiters is ready to find and qualify top of the line candidates for your clerical, customer service, legal and accounting staffing needs.