It's not a Cedrus deodara (Deodar Cedar) and not a Tsuga heterophylla (Western Hemlock), as far as I can tell. I don't think the big tree in our yard is either of the above-named.
Its shape doesn't look like either of the two photos I found in my Taylor's Guide to Trees (Houghton Mifflin, 1988), though it more closely resembles the hemlock than the cedar.
Here are two pictures of the needles on our tree, which also look different from the ones I see in the book.
Here are pictures of the C. deodara and T. heterophylla needles and cones. I don't recognize them.
I don't see any tree in Taylor's Guide that looks like the one growing in our yard. If anybody reading this can tell me what tree it is, I will be grateful.