<P> I - 10 replaced and runs concurrently with U.S. Highway 85 (US 85) from the New Mexico border up until the two diverge at mile marker 13 . The two highways parallel each other for several miles until US 85 continues to head south to the border with Mexico and I - 10 turns east towards Downtown El Paso . Prior to the Interstate Highway system, US 85 ran concurrent with US 80 from the New Mexico border until the two diverged in Downtown El Paso . When I - 10 was constructed in downtown El Paso, several blocks were demolished, and a sub-grade trench was built for the freeway . A series of overpasses now carry the preexisting north - south surface streets over the east - west stretch of I - 10 through downtown . I - 10 replaced US 80 through El Paso and to the southeast and east to the present day junction of I - 10 and I - 20 . US 80 along this route has been completely removed from the highway system in favor of I - 10 . </P> <P> At the junction with I - 20, I - 10 replaced US 290 eastward to the present day junction of I - 10 and US 290 southeast of Junction . This section of US 290 was deleted from the highway system . From this point to near Comfort, I - 10 replaced State Highway 27 (SH 27). SH 27 still exists along this stretch, mostly paralleling I - 10 to the south . From Comfort southeast to San Antonio, I - 10 directly replaced US 87 . </P> <P> I - 10 generally follows the alignment of US 87 on the northwest side of San Antonio into downtown . A new alignment was built to the south of downtown for the freeway since it was impossible to upgrade the surface streets in downtown that US 87 and US 90 followed prior to the Interstate Highway System . Southeast of downtown, I - 10 curves back to the northeast to connect with the pre-interstate alignment of US 90 . </P> <P> Construction of portions of I - 10 were well underway and completed prior to the commissioning of the highway in 1959 . The section from Culebra Road to Woodlawn Avenue opened as the first freeway in San Antonio in 1949, but was signed as US 87 . Expansion and construction continued in the 1950s, but the bulk of the construction occurred in the 1960s after the interstate was commissioned . The current alignment was completed by 1968 . </P>

How many miles is it across texas on interstate 10