first of all - don't brushoff the heavy equipment option. you say you have a gate-- how wide is it ? A wooden fence can be unscrewed and moved for a backhoe and put back. SCUT like mine can squeeze in a 4 ft gate. I dug up maple stumps that had roots deeper the 4 ft in ground. What kind of tree was it ? softwood? maple? pine? A walk behind stump grinder will fit through almost any gate. It pretty much 20 inches wide. A stump in foot diameter will be gone in no time so a 4 hour rental is all you need.
Or if time is on your side and low money, I'd go with the route other said. move as much dirt you can from sides of stump and get to cutting with a chainsaw. cut so the stump is just below the surface so you can mow over it.plan on replacing the chains a few times due to dirt.
got a axe? chip away everyday for an half hour or longer if you can stand it for a month or so, it will be gone in no time.