Remarkably, Speer has never been on the state highway system... except for the short segment between Federal Blvd and the point shown here. From 1927-1932, that half-mile segment carried US 285 traffic. Not the current US 285 that we all know and love. This was the original US 285, which ran north from Denver, essentially along modern US 287, ending in Laramie. Denver-bound 285 traffic turned off Federal and onto Speer, but at the time Speer did not continue straight ahead. Rather, at this location traffic turned due east along a no-longer-extant segment of 27th Av. After about three blocks, the road curved southeastward again, crossing the Platte River right through what is now Confluence Park, via the 14th Street Bridge (again, no longer in existence). 14th ran approximately where Speer does now, although it was slightly closer to Cherry Creek. 14th crossed to the east bank of the creek at approximately Blake St, and then resumed a southeasterly direction. US 285 went down 14th to Colfax, where it junctioned US 40. Most likely US 285 was dual-signed with US 40 east for a block or two, terminating at the State Capitol, and at its junction with US 85 (which ran along Broadway at the time).
Sources: see the maps on the US 285[i] page