Thanks for posting this.  Would you please post a photo of the completed board?  I'd like to see how you wired it up.

Another hint is if you require finer ADC resolution, (you're likely only utilising 1/3 of it) consider configuring your ADC to operate "supressed-zero". I've got an example of this on one of my projects here.  A 10 bit ADC count range 0 to 1023 would equate to 11.0 V to 16.12 V = 5 mV per bit.   

Hi, if the monitoring device is consuming a significant current because its 12 V supply is on the same supply you're monitoring the main culprit will be the 3-terminal regulator. Don't forget it consumes energy while the microcontroller is sleeping.  Power the circuit instead from a single cell lithium and let it take cycling instead.

 Whenever the microcontroller wakes up and sees RV battery voltage > 13 V  then it connects a charger from the (also charging) 12 V circuit to top up the lithium battery. Possibly a relay and even re-utilising the regulator modified as a crude charger.   

Bear in mind that if you presently reference your ADC from the 3.3 V stabilised power rail you would also need to add a voltage reference because the voltage on the lithium will typically vary +/- 0.25 V  of 4 V. 

same as my earlier comment about the FETs - the circuit will bias itself off when the ESP8266 is off

Use a P-type FET like the IRLML6402 as a hi side switch - tie the source to the voltage you wish to monitor, the drain to the resistor divider and a pair of 10K or so resistors - one between the gate and source to bias it off, and the other between the gate and the drain of a 2n7000 fet, with the 2n7000 source tied to ground, and the gate to 2  resistors, a 10k to ground, and a 1K to the micro pin that goes high to enable the divider.

Thanks for the idea.  I am now thinking of using very high value resisters to reduce the current flow and just leave them connected all of the time.  Something like 500k and 100k.  That should draw 25uA if I calculated correctly, which is nothing to a large 12v battery.  I think that will work since the input impedance of the ads1115 is many meg ohm.

Don't forget a cap 0.1uf ceramic across the lower resistor for noise suppression and to handle the current draw of the ADC during the conversion cycle.

I am trying to figure out how to engage a voltage divider so that it is not always drawing current while the ESP8266 is in deep sleep.

Look at this project. I build this with kids at the library. Control the bottom of the divider with a NPN transistor to disconnect ground when you want to do so. 

http://rsg-electronics.com/wp-content/uploads/2019/08/NightLight_006.pdf

Basically interrupt the path of the current at the bottom of the divider and only engage it when you need to do so.