The Northwoods League, in addition to being a developmental league for players and coaches, is also a developmental league for umpires. The concentrated game schedule, travel, and Minor League-like game conditions give NWL umpires a pre-professional seasoning unparalleled in all of baseball. Since the League's inaugural season in 1994, dozens of its former umpires have furthered their careers in affiliated professional baseball, including 38 that were working professional games at the end of the 2009 season. Of all of the umpires in Minor League Baseball, about 20% worked their way through the Northwoods League.
The League recruits its umpires from the two umpire schools whose curriculums have been approved by the Professional Baseball Umpire Corps. (PBUC): Jim Evans' Academy of Professional Baseball Umpiring and Harry Wendelstedt School for Umpires. The umpires ultimately chosen are often among the top school graduates who were then selected to the pre-season, PBUC sponsored Umpire Evaluation Course.
The NWL employs eight two-man crews during the regular season, a six-man crew during the mid-season All-Star game, four umpires for the divisional playoffs, and six for the championship series. Umpires are salaried and are provided hotel accommodations, meals and travel.
For an umpire, climbing the ranks from the low levels of Minor League Baseball to becoming a Major League Baseball umpire is a long and difficult journey. To date, former Northwoods League umpire Delfin Colon (2000) is the only NWL alumnus to complete that journey, but only on a part-time basis. He has umpired Major League games during portions of 2008 and 2009 as an injury/vacation replacement but continues his full-time assignment as an umpire in Triple-A for the Pacific Coast League.