Large Law Firms
Large corporate law firms make up a small but very visible portion of the private sector job market. These firms typically have a recruiting department with administrative staff to organize their hiring efforts. They also expend resources to advertise their firms to students, to be sure that you know about their practices and their interest in hiring talented law students.
These employers primarily hire 2L students for their summer programs although they may include some small number of 1L students. The proportions will heavily favor 2L students.