Semoran was initially conceived as a bypass around Orlando, combining existing roads into a partial beltway. According to "A Guide to Historic Orlando" (2006), the name was submitted by two people in a 1967 newspaper contest to name the road.
The east-west portion from Apopka to Altamonte Springs via Forest City is significantly older than the remainder south to Orlando International Airport. A public road appears on an 1890 map of Orange County (which included current Seminole until 1913) in approximately the present location of Semoran.
The road began in the "Town of Apopka City" as an extension of Fourth Street, and followed the sixteenth section line east to the present Lake Cortez Drive, where it curved slightly to the north to avoid Border Lake. Traffic bound for Orlando turned south at Roger Williams Avenue, but by 1919 the present Apopka Boulevard had been built, beginning on Alabama Avenue. Orange County's 1926 $7 million road bond issue led to the paving of this "Apopka-Forest City Road" (Project No. 45), now extending 2.35 miles from new State Road 2 (Orange Blossom Trail) to the county line at Border Lake.
From Border Lake to Forest City, the 1890 map shows a route slightly north of the current one, ending up on Calabria Avenue (then known as Jesup Avenue) in Forest City. The curving present alignment, entering Forest City on Palmetto Avenue, had been adopted by 1928, when Seminole County filed a plat (book/page 6/69) for "Apopka Road" from the county line to Maitland Avenue in Altamonte Springs.
The 1890 and 1928 alignments both leave Forest City on Orange Avenue, 1/4 mile south of Palmetto Avenue and 1/2 mile south of Jesup Avenue. Entering Altamonte Springs, the 1890 route was actually closer to current SR 436 than the 1928 route, as it ended up at the intersection of Essex Avenue and Massachusetts Avenue, the latter now SR 436 past the Altamonte Mall. The 1928 route followed the present Altamonte Springs Road and Haines Street, then turned south on Essex Avenue, east on Orange Drive, and back north on Boston Avenue to rejoin the 1890 and present alignments on Massachusetts Avenue. The Altamonte Hotel, center of the early settlement at Altamonte Springs, was located at the end of Massachusetts Avenue at Maitland Avenue, where it S-curved into Altamonte Avenue. A short horse-drawn streetcar line, operated by the hotel, ran east on this street to the railroad station (site of the future SunRail station). This was also part of the Dixie Highway between Orlando and Sanford (platted 1928 in book/page 6/54 as "Old Orlando Road"), which entered from the south on Maitland Avenue and exited on Reagan Boulevard (formerly Longwood Avenue).
It is unclear when the road from Altamonte Springs east to Anchor Road (formerly Lake Howell Road) was laid out. On the 1890 map, the way is blocked by an arm of Prairie Lake. The 1928 "Old Orlando Road" plat appears to show a road here, but no road shows up on a mid-1930s State Road Department map. It is definitely present on a 1936 (?) SRD map and a 1940 aerial photo, with a visible fill across the arm of Prairie Lake. The 1935 law quoted below refers to this portion as "the present county road".
Semoran incorporates part of the old Lake Howell Road through Casselberry. The 1890 map shows a public road coming down from Longwood on Sunset Drive and curving southeast and south along present Semoran, then southwest to end up on Phelps Avenue in Winter Park. Lake Howell Road was platted in 1928 (book/page 6/59, amending a 1925 plat on book/page 4/17), splitting from Old Orlando Road (Reagan Boulevard) at North Street in southern Longwood and following the present Anchor Road to east of Altamonte Springs. Then it picked up the present route of Semoran (a piece of the old road still exists here as a frontage road) southeast and south to the west side of Lake Howell, turning off onto what is still known as Lake Howell Road to end at "Maitland-Gabriella Road" (Howell Branch Road).
Beyond Howell Branch Road, there was no improved road in the Semoran corridor until the state built the current road in the 1960s. Travelers continuing south had to either turn east to Goldenrod and resume their southerly route on Goldenrod Road, or turn west and south through the outskirts of Winter Park.
The 1926 Orange County bond issue included what was then known as East Lake Barton Road (Project No. 79), following the present Semoran for 2.6 miles between Old Cheney Highway and Curry Ford Road. This was entirely new construction; the 1919 map shows no road in the corridor. By the 1940s, the name "Cannon Mills Road" was in use; a short northerly extension was platted in 1948 (book/page R/25). (This name seems to have come from the Cannon Mills Airport, at the northeast corner of Lake Underhill Road, which in turn was apparently named after a cotton mill in Concord, North Carolina, owned by James William Cannon. Confirmation or correction of this history would be appreciated.) But at their March 25, 1952 meeting the county renamed the entire length to Lake Barton Road, a name it would keep until 1967.
The present route of Semoran south of Curry Ford Road was also not improved until the 1960s, though Dixie Belle Drive, 1/4 mile to the west, was part of the 1926 bond issue.
The state legislature began to designate the future Semoran Boulevard as a state road in 1935, with the passage of chapter 17311, establishing a state road
Beginning at the intersection of the Lake Howell Road with State Road No. 3 [US 17-92][...] and running westerly, following the present county road to Altamonte Springs, Fla. Thence westerly following the Forest City-Apopka Road through Forest City to the west line of Seminole County, Florida. Approximately eight and one half miles.The State Road Department gave it the State Road 288 designation. In 1937 (chapter 18169) the portion in Orange County was also established
extending from a point on the Seminole-Orange County line[...], thence Westerly 2.33 miles to intersection with State Road No. 2 [US 441] at Apopka, Orange County, Florida, said road being now known as Orange County Hard-Surfaced Road No. 45, and being a continuation of a hard-surfaced road in Seminole County, Florida.Then in 1941 (chapter 20949) it was further extended east
That State Road No. 288 where it intersects with State Road No. 3, be and the same is hereby extended to connect with State Road No. 202 at or near Oviedo, Florida. [...] Beginning at the intersection of State Road No. 288 with State Road No. 3 [US 17-92][...] running Easterly eight miles more or less to the NE corner of Section 16, Township 21S, Range 31E.Note that, except for Chapel Street at the Oviedo end, there neither is nor has ever been a road on this exact alignment, which lies north of Red Bug Lake Road and south of Seminola Boulevard.
The SRD renumbered the entire state road system in 1945. The constructed portion of SR 288 became 436 (no number was assigned to the 1941 extension):
From a point on SR 500 [US 441] East of Apopka Easterly via Altamonte Springs to intersection with SR 15 and SR 600 [US 17-92].The newly-created SR 434 (no pre-1945 number, though its pieces had been designated as potential state roads in 1941 (chapter 20296)) is also relevant to the history of SR 436:
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.This incorporated very little of the present SR 434. It began on SR 436 a mile east of the county line, following Bear Lake Road and Bunnell Road to Forest City. Then it used the present SR 434 (and its former alignments on Sanlando Road and Warren Avenue) to Longwood, where it turned south on Old Orlando Road (Reagan Boulevard). The entire length of Lake Howell Road (including a short overlap at SR 436's east end) and the majority of Maitland-Gabriella Road (Howell Branch Road) took it to SR 426 at Goldenrod.
Both of these routings can be seen, unchanged, on a 1951 Seminole County map (reprinted 1955). Note that two realignments had been made since the 1920s, eliminating turns on SR 436 at Forest City and Altamonte Springs and leaving behind Orange Avenue and Altamonte Springs Road-Haines Street-Essex Avenue-Orange Drive-Boston Avenue. It's not entirely clear when these changes happened; grading is visible on a 1940 aerial photo and construction is complete in 1947, but it may have been temporarily delayed by World War II. (It's interesting to note that, between the two relocations, a new road was built just north of the old road. All of this has, of course, since been wiped out by widening.)
Back in Orange County, the state legislature designated most of the 1926 bond issue roads as potential state roads in 1939 (chapter 19049). (The list included Project No. 45, already designated in 1937 as an extension of SR 288.) Project No. 79 became SR 438, but, like most of the 1939 additions, did not receive a number in the 1945 renumbering. However, unlike most of them, it was later taken over by the state: a 1950 Orange County map (reprinted 1954) shows it as part of SR 526. This route had been defined in 1945 to end at the west edge of the Municipal (now Executive) Airport, was soon extended south and east around Lake Underhill (including Project No. 80), forking both north and south at the Cannon Mills Airport to termini at (new) SR 50 and Curry Ford Road (soon to be taken over as SR 526A).
As early as 1956 (April 17 meeting minutes), a "Perimiter Road"[sic] was being proposed by Orange County to connect the Casselberry end of SR 436 to SR 528, incorporating the north-south portion of SR 526. By 1963 (September 23 meeting minutes) the SR 436 designation had been assigned north of SR 50, but it was to remain SR 526 south to SR 528 for several years. Incidentally, by 1960 (Seminole County map) the Casselberry-Goldenrod road was part of SR 436 rather than SR 434; the Howell Branch Road portion may have become SR 436A upon completion of the new SR 436. The new four-lane Lake Barton Road was (nearly?) done by 1967, when the Semoran Boulevard name was chosen.
The new alignment left the old Lake Howell Road near the west shore of Lake Howell, and cut diagonally southeast to just north of Aloma Avenue (SR 426), where it returned to a southerly heading. About halfway to SR 50, an S-curve took it west to line up with the older Lake Barton Road, along which a line was drawn straight south to SR 528 at the McCoy Jetport. SR 528 itself was being widened to four lanes as part of the Bee Line Expressway project, which had temporarily used an improved McCoy Road rather than a full freeway past the airport. In 1983 an interchange replaced the at-grade intersection of SR 436 and SR 528, which also served as the main entrance to the airport after it was relocated east in the 1970s.
Part of the east-west portion of SR 436 remained two lanes into the 1970s, but eventually saw widening to match the remainder of the partial loop. Since then the entire road has been six- and eight-laned, with the part from Curry Ford Road south to SR 528 coming last in the mid-2000s.