There are:
Twin Rocks
Pike's Basin
Tumbleweed
Gaptooth Breach
Fort Mercer
I believe that are all in New Austin

Treasure Map 1

Located at the Hanging Rock which North North East of Armadillo. Simply walk to the side of the rock opposite of the tree with a noose and viola!

Treasure Map 2

Located near lake Don Julio which is directly south of Armadillo. Open your map. South of the lake there is a black square located in the bluffs on the map (Not the one directly bordering the lake). This is your first clue. Once you've found the house look at the cliff to the south. Climb cliff to the camp site. Nearby is a feverfew plant, south of that is a very steep cliff. Carefully slide down twice and look for pile of rocks.

Treasure Map 3

This one is easy. Simply head to the town of Tumbleweed which is far west of Armadillo. Look for the big mansion on the western part of town. Go to the basement and look for the cow skull.

Treasure Map 4 (Tubman's Gold)

You can not find this treasure until you have completed the main story mission “We Shall Be Together in Paradise” as that allows you to travel to Mexico. Go to the town of Chuparosa. It will the town with the “LR” story mission icon. Directly North of the town head to the river. Travel along the small road that follows the coast traveling East. On your map the road will be bordered by two lines on either side of it. The tree with the skulls is located there. Make your way down past the broken wall toward the river and it will be buried to your right.

Treasure Map 5 (Brown's Gold)
This treasure is located to the East of Punta Orgullo. You are looking for a large jutting rock structure. There is a green house for sale on your map that should be on the river. Look directly south of the house about half way between it and the main road. It will be the tiny cluster of rocks on your main map. Simply climb the rock to the top and claim your treasure. Note there is a chest at the base of the rock as well.

Treasure Map 6 (Douglass' Gold)
This one is easy. Located far south of Chuparosa, you are looking for a huge Rock Archway called Ojodel Diablo. Travel south and you can't miss it.

Treasure Map 7 (Garrison's Gold)
Another one that in the middle of nowhere. Find Roca de Nadera on your map. (West of the town Casa Madrugada in between the Diez Coronas and Perdido regions.) From Roca de Nadera go west to where the river bends. Look for the odd shaped rock shown on the treasure map, it will be close to the river. Once you find it go west of the rock over a small road and hug the cliff. You have to walk a for a little while along the cliff to find it. Be careful of falling off and you should end up almost directly North of Agave Viejo if you look at your main map.

Treasure Map 8 (Picketts' Gold)
You will not be able to find this treasure until you complete the main story mission “An Appointed Time” where you unlock West Elizabeth. Once you have this one is really easy to find. You're looking for Broken Tree which is off a main road in the Great Plains leading towards the town of Blackwater. On your main map look for the Buffalo icon and what looks like a Gazebo, (Beecher's Hope) on that road is where you'll find the Broken Tree. There aren't any other trees around so it will be easy to spot.

Treasure Map 9 (Stonewall's Gold)
You guessed it you're going to the mountains! Start heading towards the Northern mountain range. Follow the road that circles Tall Trees. You're going to end up in between the Aurora Basin and Nekoti Rock. Along that road you'll reach a T-intersection that has a path leading North up a mountain. On your main map this will roughly be right above the “T” in Tree for “Tall Trees”. Continue up the winding road until you reach a plateau. Up against the edge of the mountain lies a cave. Inside you will find the last treasure. Congrats treasure hunt

The ending is different then you might expect. If you know at the beginning of each mission whether or not it is the last you will spoil the tension Rockstar tries to create. Don't look unless you really must.

Spoiler:

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