This multi-branched spur line was first built in the 1940s by the Atchison, Topeka and Santa Fe to serve both farmers in the area and Luke Air Force Base. The spur split from the AT&SF mainline in El Mirage at a junction called "Ennis Station", and then zig-zagged its way for 12 miles to Waddell and McMicken, both unincorporated communities west of Phoenix. These endpoints once served produce distributors, who would load their fresh produce onto reefers.
Over time, parts of the line fell into disuse for the usual reasons: urban development, the switch to road trucks, etc. As of 2010, BNSF still uses parts of the spur to serve four online customers, with an average of one train per day visiting the area; the rest of the spur has been abandoned, with sections of track removed. However, active tracks still reach as far as Fennemore, about 9 miles from Ennis Station.
According to some news articles from 2008 in the Phoenix Business Journal, the area around the spur is ripe for more business and industrial development, and BNSF is planning to capitalize on the expected growth by refurbishing a majority of the line in order to serve the influx of potential customers. They expect that traffic along the spur will increase within the next few years.
The interactive map shows the Ennis Spur in its entirety.