Theme: Friends - Although there are circles, it's doubtful they helped in solving.
39A. Close associates, and a hint to this puzzle's highlighted squares : CIRCLE OF FRIENDS
1D. 39-Across, in slang : PEEPS. Short for the people one considers friends or close pals.
57D. 39-Across, in slang : POSSE. Short for the people that congregate around a leader of sorts.
Argyle here. Starting at 12 o'clock, PAISANO, COMRADE, BRO, and AMI. Friends around the orb. Four beefy corners to the puzzle. Ellen Leuschner is a new name to us; hope she stops by.
Across:
1. Aerospace giant __ & Whitney : PRATT
6. Oft-mispunctuated word : ITS. or is it IT'S?
9. Bravery in battle : VALOR
14. Like a foggy graveyard : EERIE
15. Letters in a graveyard : RIP. Finding regular letters in a graveyard might be considered EERIE.
16. Love a lot : ADORE
17. Name on a WWII bomber : ENOLA
18. Brewpub offering, for short : IPA. (India Pale Ale)
19. Actress Watts : NAOMI. Here with her little buddy.
20. Garden mulch : PEAT MOSS
22. Monkeylike : SIMIAN. or King Kong like.
23. Evening in Parma : SERA. Parma is near the top of the Italia boot.
24. Like shrinking violets : SHY
25. Fashion-designing twins : OLSENS. Famous for being famous.
26. "Conan" channel : TBS
28. Puerto Rico, por ejemplo : ISLA
29. Musical genre related to punk : EMO
32. Actor Quinn : AIDAN. Captain Gregson on TV's "Elementary"
35. Startle : ALARM
42. Become sour : GO BAD. But not bad if talking about some pickles.
43. Hard to startle : STOIC. Really?
44. Granola grain : OAT
45. Brest beast : BÊTE. As in bête noire.
47. Eponymous guitarist Paul : LES. Many guitars bear his name.
49. Smartphone feature : CAMERA
52. Vino opener? : VEE
54. Show appreciation, in a way : CLAP
58. Exaggerate : OVERDO
59. Legendary city of gold : EL DORADO
61. Heaven-sent food : MANNA
62. Usher's offering : ARM
63. Angler's bucketful : WORMS
64. Heaps : PILES
65. Pennsylvania, for one: Abbr. : AVEnue
66. Singer Costello : ELVIS
67. Slow-moving arboreal critter : SLOTH
68. "On __ Majesty's Secret Service" : HER
69. Blue-gray : SLATE
Down:
2. Three-time Golden Globe winner Zellweger : RENÉE
3. Riotous, as a crowd : AROAR
4. Charge, in a joust : TILT AT
5. Jets, Mets or Nets : TEAM
6. From Donegal, say : IRISH. Although born in Chicago, Aidan Quinn had Irish parents and spent time growing up in Ireland.
7. A bit buzzed : TIPSY
8. Place to chill : SPA. 62D. "Yeah, that's the spot!" : "AAH!"
9. Rapper whose name sounds like a dessert : VANILLA ICE
10. Water, facetiously : ADAM'S ALE
11. Sarge's superior : LOOIE. (Lieutenant)
12. Finance guru Suze : ORMAN. Often seen on PBS.
13. Buckboard controls : REINS
21. Davis who was married to Ruby Dee : OSSIE
22. Letters in the sand, perhaps : SOS. On a deserted isla, ok; in a cemetery, eerie.
27. "Horsefeathers!" : "BALDERDASH!". A nice long entry partnered with Vanilla ice. Hmm.
28. Facts and figures, for short : INFO
29. Heart chart: Abbr. : ECG. (electrocardiogram)
30. "O Sole __" : MIO
31. Mars or Venus : ORB
33. Two pills, e.g. : DOSE
34. Toward the back of the boat : AFT
36. "It's __-brainer" : A NO
37. Nutritional qty. : RDA. (Recommended Daily Allowance)
38. Hours in Tempe, Ariz. : MST. (Mountain Standard Time)
40. Popular wine grape : CABERNET
41. Hot under the collar : RILED
46. Lao Tzu's "path" : TAO
48. Move with a mouse wheel : SCROLL
49. Freebies : COMPS. Items received free of charge, complimentary.
50. Be of help to : AVAIL
51. __ Park, N.J. : MENLO. Thomas Edison set up his home and lab on the site of an unsuccessful real estate development, "Menlo Park".
52. Enthusiasm : VERVE
53. Toon hunter who has twouble with some wanguage : ELMER. Bugs called him, "poor little Nimrod".
55. Immature insect : LARVA
56. Let in or let on : ADMIT. Neat clue.
60. Is in the red : OWES
Argyle