SR 434 was defined in the
1945 renumbering as
from a point on SR 436 South for approximately one mile then Northeast to Forest City, thence North and Northeasterly to Longwood, thence South to intersection with SR 436 East of Altamonte Springs; thence Southeasterly to intersection with SR 426 South of Gabriella. SR 431 was defined as
from a point on the old Orlando-Apopka Road near the N.E. corner of Section 4, T. 22 S - R. 29 E. Northerly to intersection with SR 436 at Forest City The original route of SR 434 had it begin at
SR 436 and Bear Lake Road, run south on Bear Lake Road, northeast on Bunnell Road, along the current SR 434 to
Longwood, south on
CR 427 and Anchor Road, southeast on current
SR 436, south on Lake Howell Road, and east on Howell Branch Road to end at
SR 426. At some point, Alafaya Trail from
Oviedo south to
SR 50 was added as an extension of
SR 520. Also around the same time, SR 434 west of
Forest City and east of
Longwood was removed, and SR 434's east end was extended to
SR 419. Eventually, around 1985, SR 434 was extended in both directions, south from the west end along
SR 431 and east and south from the east end along
SR 419 and
SR 520 (which had, in the meantime, become
County Road 520 on Alafaya Trail). In 2013, a short extension of SR 434 opened, connecting the road directly to
SR 423 (John Young Parkway) via a flyover bridge across
U.S. Route 441 (US 441 or
Orange Blossom Trail). A major goal of this extension was to alleviate I-4 traffic. On June 2, 2018, a section of SR 434 in Oviedo was closed after an old drainage structure below the road collapsed and caused a wide hole to open up. The road reopened to traffic on June 8, 2018 after repairs were made. ==Major intersections==