While a young DC3 first officer, I recall being told that the spar was just two end-sections, held abutted together by these nuts and bolts.
Well, there's a little bit more to it. There are three spars in both the outer wing and centre section. Each one, top and bottom has a butt plate at the end of the caps and there are compression angles and waffle plates between the spars as well as a diaphragm to even out the load. Then you have some substantial doublers under the wing attachment angles themselves. The wings are held on by those 1/4" bolts around the chord, no others.
I seem to remember Northropp having something to do with the DC3 multi-cell wing design.