The Largest States (in EVs) by CD

[King]

They will all likely be the last, but which one first of the last?

[Hitchabrut]

I'd go with IL.

[nclib]

I'd say CA, because the 2000 CD results came in rather quickly.

[minionofmidas]

It should be California...at least their district boundaries take cities into account somewhat, which should make calculating these things a tad easier.
PA or OH would also be possible by that standard.

Then again, this is probably more to do with state policy than with any sort of difficulty, so I won't vote in the poll.

[ElectionAtlas]

Of this list, only CA actually reports results for President by CD.  The rest have to be calculated from the precinct data by outside interested parties.