Poncha Junction marked the point at which the Marshall Pass line turned south out of the valleys west of Salida and headed up the Poncha Creek drainage. The Monarch Branch continued to the west. The junction wye was located just to the northwest of the town of Poncha Springs, CO.
The D&RG reached the site of Poncha Junction in November of 1880, but the site didn't become a junction until the construction of the first part of the Monarch Branch the following year. The Marshall Pass (and connecting Valley Line) were abandoned in the early fifties (1951 for the Valley Line, 1953 for Marshall Pass), and by 1955 there were no rails south of Poncha Junction. The remaining mainline to the east, all the way back to Salida, became part of the Monarch Branch and was all standard gauged in 1956.
With the shutdown of CF&I's blast furnaces in Pueblo in 1982, limestone from Monarch was no longer needed, and the rails were abandoned in 1984. Nothing remains of Poncha Junction today except the grade itself.