If you're looking for a meeting place or a good stop around ½ or halfway between Casa Grande and Yuma, you can try Tartron, AZ, which is a little over 1 hour west of Casa Grande, or about 1½ hours east of Yuma.
Other possible places to stop near the midpoint include Sentinel, and Stanwix.
About ¼ or a fourth of the way, you can stop at Big Horn, AZ. This is about half an hour west of Casa Grande.
About ⅓ or a third of the way, you can stop at San Lucy Village, AZ. This is almost an hour west of Casa Grande.
About ⅔ or two thirds of the way, you can stop at Stoval, AZ. This is about 1½ hours west of Casa Grande, or almost an hour east of Yuma.
About ¾ or three fourths of the way, you can stop at Owl, AZ. This is almost 2 hours west of Casa Grande, or almost an hour east of Yuma.
If you drive straight through without stopping at all, the total distance is 178 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 2 hours, 32 minutes.