Jane Ross opened the scoring for City, before Jill Scott added a second. Ross grabbed the third before the break, while Georgia Stanway's stunner made it four.
Jess Clarke's early second-half spot-kick sparked hopes of the most unlikely comeback, but Izzy Christiansen rounded off the scoring with a superb volley.
Super start for City
The hosts were slow to start and were immediately punished by City. A cross that had went over everyone in the box eventually fell for Christiansen, who made her way inside only to be stopped by Leanne Crichton. But a lack of communication meant the ball sprung free for Ross, who poked a fine finish past Megan Walsh in goal.
County did try to respond as Ellen White fired low and hard at goal, yet it was easy pickings for Karen Bardsley. Instead, City continued to press. The Lady Pies were finding it tough going dealing with set-pieces, as well as Nikita Parris' build-up play. Her flick on found Scott racing through, though the midfielder failed to hit the target.
Scott didn't have to wait long to make up for that initial miss, as a wonderful corner routine paid dividends. Taken short and then set for Megan Campbell, the Republic of Ireland defender whipped in a superb ball to Scott. She rose highest and, unmarked, to loop a header over the defender on the line and despairing Walsh.
Blues heap more misery on Notts
The game was proving to be a physical affair and one which both Lucy Bronze and Scott were feeling the full effects of. The former had to go off for treatment after catching Crichton's stray elbow, while Parris, Scott and Amy Turner were all struck by each other in a nasty collision. Thankfully, all were okay to continue.
There would be no stopping Scott, however, as she played her part in City's third. A wonderful, fast-flowing counter saw the midfielder at the head of the attack and doing well to hold the ball up for the oncoming Ross. The Scot collected the pass before jinking inside and unleashing a curling strike that found the top corner.
That was top corner, but the fourth goal of the game was right in the postage stamp. A corner wasn't cleared with the gusto County needed and Stanway made them pay in emphatic fashion, rifling home from 20 yards with Walsh powerless to prevent it going in. That capped off a stunning first half for the visitors, who held a four-goal lead.
County respond, but injuries are the main worry
Whatever was said at the break in the home dressing room worked a treat, as County looked more lively than they had done in the entirety of the first-half. They were rewarded, as well, with Rachel Williams being fouled by Steph Houghton in the area. Clarke stepped up and confidently sent Bardsley the wrong way.
The higher tempo from Rick Passmoor's had stifled the City attack but they were still able to break down their opponents on the odd occasion. Parris was played through on goal with a well-timed pass, only for an unnecessary final touch to force a poked shot that was well dealt with by Walsh in the County goal.
Much like the first half, the game was fair and physical but two players were not as fortunate as those in the first half. Abbie McManus was stretchered off after a nasty fall on her ankle, and a clash of heads between Fern Whelan and Parris resulted in the former seeing nearly 10 minutes of treatment before being braced and replaced.
Christiansen adds gloss with a super strike
City seen out the remainder of the game with very little trouble, and added a fifth through Christansen's special strike. Once again the hosts failed to clear their lines, and a touch of class and composure to control a dropping ball. She then sent a stunning volley past the outstretched Walsh and into the top corner.
Clarke and Steph Houghton traded late chances, but the damage had already been done in the first-half. City went a point clear of Chelsea at the top of the WSL table as a result, and also have a game in hand over the Blues. As for County, they are still embroiled in a mid-table battle.