I'm sure most of you know of this work by Shelby Stanton, but I was recently told to check it for information on my father's WW2 service. It was recommended to me by Mr. Leroy Good, who is the president of the 473rd Infantry Regiment Association. Most of my father's records, like many others, were destroyed in the St. Louis fire in1973, so it has been difficult to recreate the progress of his service. I just got a look at a copy of Order of Battle, and I was stunned. I learned more about my father's units in 20 minutes than I have discovered in years of looking. For any other newcomers looking for unit information in the US Army, I highly recommend this book. It's expensive to purchase, but I borrowed one through my state library system. It is an invaluable resource for this kind of information.
I bought my copy about 18 years ago. The dust jacket bit the dust a few years ago. It is well worth the cost. I also have his Vietnam Order of Battle. Used to catch a guy lying about his service. Claimed he was a Ranger, until he could not come up with a correct unit number.