Complex sentence: When a shortcut was built between the crossing of the Rio Grande at Mesilla and Cooke's Spring, as part of a military road construction project in 1856, wagon traffic soon diminished on the longer route by way of San Diego Crossing.
Split into simpler sentences: When a shortcut was built between Mesilla and Cooke's Spring, as part of a military road construction project in 1856. Traffic soon diminished on the longer route by way of San Diego Crossing.