Ryan ten Doeschate's team put themselves on the brink of the title by thumping Warwickshire by an innings inside three days at Edgbaston on Thursday but had to wait for the result from Taunton, where second-placed Lancashire were in action.
A seven-wicket win for Somerset means Essex, with eight wins under their belt, cannot be caught, even with two games to go.
It is their seventh title, all their previous successes coming between 1979 and their last one in 1992 when they retained the championship during the all-conquering years of England stars such as Graham Gooch, Nasser Hussain and Derek Pringle.
Coach Chris Silverwood said he hoped his players could build a legacy to match former club greats.
"Everyone talks about the (Keith) Fletcher era with Essex," he said.
"What I would love people to be doing in 20 years is talking about this era. Your Jamie Porters, your Dan Lawrences, your Tom Westleys. I want them talking about them. If they do that it means we've left a legacy behind and what more could you ask for?"
First Published: September 15, 2017, 5:23 PM IST