I had completed every single quest in Holland Valley (including the lighters and comic books) and was only 51/52 quests. I finally figured out the
Prepper's Stash, O'hara's Haunted House counts toward Holland Valley although it is actually in the Henbane River region. When i finished the stash quest i was given credit for my 52nd and final quest in Holland Valley. I hope this helped you finish your quests too!
P.S. ~ If you have done the Haunted House and are
still missing a quest, go
shoot down a part of the giant YES sign in the Northwest part of Holland Valley and it will give you a quest to finish destroying the sign. Don't worry if it takes a while to destroy, each sign peace has a lot of health.
I would reccomend explosives or airplane guns to easily complete the quest.
All 52 quests in Holland Valley are below:
Story Missions: (Not in order of completion)
1 - No Means No (Destroying the big YES sign)
2 - Man's Best Friend
3 - Fall's End
4 - Air Raid
5 - The Cleansing
6 - Razing the Steaks
7 - Blow Their Mine
8 - The Widowmaker
9 - Jumping Ship
10 - Good Samaritan
11 - The Atonement
12 - Hit The Gas
13- The Scattered Flock
14 - The Quality of Mercy
15 - Wrath
16 - The Confession
17 - Death Wish
19 - The Revelator
20 - Grace Under Fire
21 - Wingman
Side Missions: (Not in order of completion)
22 - What They Carried
23 - Golden Age of Nostalgia
24 - The Hero's Journey
25 - The Judge Moose
26 - Valley Armed Convoy
27 - Water Works
28 - Cow Punching
29 - Bear Necessities
30 - Exodus
31 - Uncrate
32 - Baptism of Fire (Clutch Nixon Stunt Drive)
33 - Out of this World
34 - Special Delivery
35 - Free Larry
36 - Patriot Acts
37 - Test Festy
38 - Spray and Pray (Clutch Nixon Stunt Fly)
39 - Prairie Oyster Harvest
40 - Close Encounters
41 - Light'em Up
Prepper Stashes: (Not in order of completion)
42 - D.I.Y. and D.O.A.
43 - High Tension
44 - Swingers
45 - Fire in the Hole
46 - Deep Dive
47 - O'Hara's Haunted House (This quest is actually in Henbane River/Faith's Region but gives credit for Holland Valley)
48 - Playing with Fire
49 - Vespiary
50 - Foxhole
51 - Man Cave
52 - Long Range Lockpick
52 - Dumpster Diving