Matty Pearson's first-half header proved enough to see off a Shrimpers' side who only really tested the Town's defensive qualities in the last 20 minutes, when James Shea made his only save of note and the goalscorer and his centre-half partner Sonny Bradley headed away every ball thrown into the box.
Interim manager Mick Harford masterminded a second win in his three league games in charge so far, following the 1-1 draw at third-placed Sunderland, to take the Hatters to their highest league position since relegation from the Championship in 2007, but top spot in the third tier for the first time since the title-winning season 2004-05.
Harford named an unchanged matchday squad from last week’s 4-0 home win over Peterborough, knowing that avoiding defeat would make it the best unbeaten league sequence since the 19 set over the end of 1968-69 and start of the 1969-70 campaign.
The starting line-up had Shea in goal behind a back four of Jack Stacey, Pearson, captain Bradley and James Justin.
Just ahead of them, and returning to an old stomping ground, was former Shrimpers midfielder Alan McCormack, with Andrew Shinnie, Pelly-Ruddock Mpanzu and Luke Berry completing the diamond behind front men James Collins and Kazenga LuaLua.
The bench was also exactly the same as a week ago, with Dan Potts, George Moncur, George Thorne, Aaron Jarvis, Lloyd Jones, Alan Sheehan and goalkeeper Harry Isted.
The game started very evenly, with the hosts content to let the Hatters have the ball at the back then trying to pounce on the counter attack when moves broke down - although the Town dominated possession.
Stacey was proving the best outlet down the right, and having already blazed one attempt over the scoreboard after good work by Mpanzu, the full-back broke through in the 19th minute to latch onto a lovely pass from Berry, but home keeper Nathan Bishop raced off his line to deflect the final shot inches wide.
The breakthrough came in the 29th minute, and it was the Town’s first headed goal since Danny Hylton completed his hat-trick against Accrington in late October, Pearson breaking free of his marker to stoop and direct Justin’s right-wing corner past Bishop for his fourth goal of the season.
Southend’s first effort on goal came four minutes later, but Stephen Humphrys’ header looped tamely into Shea’s gloves after Sam Hart’s left-wing cross had proved just too high for Bradley.
Town continued to dominate the ball, although Southend were starting to threaten on the break, Sam Cox wriggling free on the right side of the area only to see his low cross cleared, before Elvis Bwomono’s deflected centre from the same area had Shea scrambling to prevent a corner.
The Hatters began the second half well and almost doubled the advantage a minute in when Justin's free-kick found Bradley unmarked at the far post, but Bishop did well to save his left-footed volley at the foot of his post and prevent the ex-Plymouth man netting his first goal for the club.
LuaLua was starting to revel in the open space down the side of Southend's three centre-halves, jinking his way past John White and standing up a delightful cross that Michael Turner did well to turn behind for a corner under pressure from Collins.
LuaLua and Collins both played a part in the next positive move for the Town, together with Justin, helping tee up the outstanding Berry, who dragged his shot from the edge of the box well wide after a period of sustained possession.
A minute later, one short of the hour mark, Justin bent a shot just over the bar from 20 yards, then Southend started to have a spell of pressure, without creating a clear-cut chance.
The next of those once again fell to the Hatters, LuaLua teasing Bwomono on the left and delivering another inviting centre for Collins, whose header looped up onto the roof of the Shrimpers' net.
Shea was called into real action for the first time in the 72nd minute when Cox let fly with a beauty from 25 yards that the Town keeper did well to fly across his line and push around the post, as he looked to preserve a 13th clean sheet in 20 league and FA Cup matches.
At the other end Collins was off target again in the 76th minute after more fine work from Justin, who was having a blinder down the Town left, the top scorer firing over from 12 yards.
Southend started to mount some late pressure, raining balls into the Hatters penalty area - but the defence stood firm to ensure that Tuesday's top-of-the-table clash with Portsmouth will kick-off with the Town in pole position.
What a night it promises to be under the Kenilworth Road lights!
TOWN: Shea, Stacey, Pearson, Bradley ©, Justin, McCormack, Mpanzu, Shinnie, Berry, Collins, LuaLua (Moncur 86). Subs: Potts, Thorne, Jarvis, Jones, Sheehan, Isted.
Yellows: Stacey, McCormack
Goals: Pearson 29
SOUTHEND: Bishop, Bwomono, Turner, Dieng, Cox, Yearwood (Kelman 69), Mantom © (McLaughlin 84), Moore, Humphrys, Hart, White. Subs: Kightly, Klass, Robinson, Kelman, Hutchinson, Smith (GK).
Yellows: Yearwood, Hart
REFEREE: Thomas Bramall
ATT: 8,460 (2,037 Hatters)
