Looks like a Gray Hairstreak, Strymon melinus.

Here is a link that might be useful: Gray Hairstreak, Strymon melinus

It's got to be a gray hairstreak, Bob. White-M hairstreaks have a white dot on the edge of the hindwing, which appears right in the middle of their wings when they're up, like yours is - I don't see a white spot. Plus, yours has two orange spots instead of one red or orange one, like W-M hairstreaks.
Gray hairstreaks are highly variable, sometimes having a "M" on their undersides. I made a picture of a gray hairstreak this past fall - you can see the orange dashes on this one, which is also a sometimes characteristic of the butterfly -
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And here's an older picture of one with something of a "M" on its underside -
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Beautiful picture, as usual!
Sherry

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White M side shot

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White M rear shot

Thanks to you both! I have been generating a Butterfly gallery and I have had this one ID'd as a Gray Hairstreak but doubts were creeping in because all my others had at least a sliver of orange on the inward side of inner dashes. You have made me more comfortable!

I hope the winter weather has not served you too badly!

Bob

great pics Bob & Sherry,

I never realized other butterflies besides the monarch liked the nectar from tropical milkweed. In Minnesota, it's just monarchs and wasps.