[jsaklas]

I'm a retiree, so I have time, but limited expertise.

There is a knocking sound (sort of a thump, thump, thump....) that sounds like it is coming from the driver's side front wheel. As best as I can tell, the sound occurs at all speeds. It is very faint for the first mile to two, then gets louder. It seems to disappear when the car is not going straight, i.e., I don't hear it when I'm making a right or left hand turn or even in a curve in the road.

I've taken off the wheel but I can't see anything in particular that is wrong - can you Cruisers help?

 

[ImperialCrown]

Welcome to Allpar. If you've had the wheel off, then you've made sure that the lug nuts are tight on that wheel. I would still check the other wheel lug nuts for tightness.
A worn tie rod end or ball joint can make noise when it isn't 'loaded' (i.e.- the play shows up when it 'floats').
Since it 'thumps' while you are driving straight, it sounds like it is related to the revolving wheel. Have the tires been rotated lately? Any 'lump' on the edge of the tread area that may be hitting the pavement going straight and less so when the car is cornering?