The Sandbox Mode allows you to play in pretty much any region of the game you want to play in - the region you choose often having a heavy influence on the various industry that will be good successes for you as you play.
Each Region can actually have several choices available for starting - and a sampling of the Regions that are available in Sandbox Mode include:
Butte: Normal Climate / Foothills / Boundless Lot Size / Lots of Metals
Colusa: Normal Climate / Plains / Large Lot Size / Lots of Metals
Mendocino: Normal Climate / Plains / Boundless Lot Size / No Metals
Sacramento: Normal Climate / Plains / Large Lot Size / Lots of Metals
Sutter: Normal Climate / Plains / Boundless Lot Size / Lots of Metals
Yolo: Normal Climate / Plains / Huge Lot Size / No Metals
Yuba: Normal Climate / Foothills / Boundless Lot Size / Some Metals
Check out each of the selections for a given Region prior to starting your game to determine if one part of the Region may not be more advantageous than another - that counts particularly for the presence of metals.
Sandbox Mode Start Options At the start of Sandbox Mode you are prompted to select one of three starting benefits - which one you choose is going to have significant impact on both how well your game unfolds, and how quickly you are able to accomplish certain goals.
The three starting options are:
1. Easy Living: start with $5,000 and plenty of resources. 2. Likes a Good Challenge: start with $2,000 and several buildings. 3. Grizzled Veteran: start with $1,000 and a few tough pioneers.
Of the three options if you are new to the game or not very well experienced, the middle one is the one that makes the most sense. The reason for that is simple: the buildings that it starts with tend to apply to the goals you have and so are a valuable jumpstart. The money is middling, but that's OK.